Mobile SIM Only Plans

Traditional pay as you go (PAYG) phones used to be the only alternative for customers who didn't want to sign up for a long, ongoing contract with a mobile phone provider.

Users buy a handset and top up with credit as and when needed. Each minute, text and MB of data is charged as it is used.

These types of traditional PAYG deals are still available, yet the prices for making calls, sending texts and accessing data are often high compared to the new style of PAYG which involves packaging services together.

With PAYG bundles, you pay in advance as you would with a traditional PAYG phone and SIM. However, services are bundled together, meaning better value for customers.

Bundles generally last for a month, after which they time out and you'll need to purchase another one to continue actively using your phone.

When people talk about pay as you go SIM choices, it's likely they're referring to bundles rather than traditional PAYG models. That said, occasional mobile phone users may prefer the true PAYG model where they only pay for what they use.

Both options often come with a free pay as you go SIM that you can obtain from the provider of your choice. You can filter the options above to show every pay as you go SIM on offer from UK mobile network providers.

Pay monthly SIM deals are an ongoing contract that can only be cancelled after a minimum term. While traditional mobile phone contracts often have a minimum term of 24 months (sometimes 18), a SIM only contract can be much shorter, usually 12 months or even just 1 month.

One month rolling contracts can be useful if customers are reluctant to be tied into a long-term contract. These can usually be cancelled with 30-days or one calendar month notice.

Pay monthly SIM only plans differ from the PAYG model described above in that customers sign up to a direct debit. They can cancel this direct debit after the minimum term of the contract is up, but a direct debit must be set up.

For some customers, this poses a problem as their credit history may not be good enough to sign up for even a rolling monthly contract. This is one reason why traditional PAYG models are an enforced choice for some customers.

That said, a rolling SIM only contract may help build up a customer's credit rating if they're accepted for this form of credit. It is also, as mentioned above, a more economical way of accessing SIM only deals.

Contracts of 12 months or more offer the best value for pay monthly SIM customers. However, many would rather not be locked in to a contract for that length of time.

It's worth remembering, too, that all SIM only mobile phone deals rely on customers either having a handset they're happy with already or perhaps picking up one second hand.

If customers sign up to a contract of 12, 18 or 24 months, they may be forced to buy another handset if theirs stops working. While this needn't break the bank, it is still an expense to bear in mind.

Finally, some of the best deals are on networks that also provide broadband services, and are reserved for their own customers as an extra incentive to bundle broadband and pay monthly SIM deals.

Most providers now offer a trio SIM card which allows customers to use the type of SIM suited to their handset without the need for reordering.

When smaller SIM card variants first appeared on the market, customers could be left without service for a few days while changeovers took place. Processes have become more streamlined and the trio SIM adds to the simplicity.

Modern SIM cards come with three sizes of SIM: Standard, Micro and Nano. There are no technological differences between the three versions - the size of the plastic casing is the only physical difference.

Handsets vary on which type of SIM they use, so check carefully before you try to install a SIM card. Attempting to insert a SIM card that isn't right for the phone could damage it.

There are adaptors you can buy which will fit a smaller SIM card into a handset that requires a larger one. However, these adaptors can also cause damage to SIM cards so be careful when handling them.

Older handset models are most likely to require Standard SIM. Newer handsets are designed to be slimmer, meaning they often use smaller SIM cards which save space.

While many of the newest handsets use Nano SIMs, this isn't a set rule. If in doubt, check the instruction manual for a phone to work out which size SIM card is needed before splitting a Standard SIM down to become a Micro or Nano.

It's also worth remembering that SIM cards issued by operator Three, can't be used in handsets that aren't 3G or 4G enabled as they don't operate any 2G infrastructure in the UK.

The four major networks (Three, EE, Vodafone and O2) all offer SIM only plans. In addition, other popular providers such as BT Mobile, Sky Mobile, Plusnet Mobile, Tesco Mobile and GiffGaff also have SIM only mobile phone deals.

It's important to know the difference between mobile network operators and mobile virtual network operators that use their infrastructure.

In the UK, the four major carriers highlighted above operate all the country's data spectrum. It is then leased by mobile virtual network operators. This means that all mobile providers apart from those four will have a host network.

To give some examples, Lycamobile's host network is O2, while iD use the Three network and Virgin Mobile use EE. As BT is the parent company of EE, their coverage and that of its subsidiary Plusnet Mobile use the EE network too.

This might seem like a technical issue that won't have much bearing on a customer's experience but remember that signal coverage across the country isn't universal.

Customers often report "blackspots" in locations they spend a lot of time in such as their home or workplace. If the network signal doesn't work in those locations, their phones are useless while they're there.

When you're choosing which network to go with, make sure you check whether the signal of the host network is going to be strong enough in the locations you spend most time in.

Along with this, work out whether the allowances on a deal are going to be wasted. Many people choose SIM only contract deals with more minutes or data than they will use. Assess your usage first and save money on SIM only plans.

For customers with a tablet or iPad, a data SIM plan which doesn't include any minutes or texts may be the best option. A tablet SIM deal or iPad SIM deal will include data without any additions that won't be used.

A data SIM plan is a good choice if customers have purchased a tablet outright or perhaps bought a second-hand one and simply need a 4G SIM to go along with it.

Equally, if a customer has come to the end of a contract, a pay monthly SIM on a rolling contract may be the best value option.

As with SIM only plans for mobile phones which include minutes and texts, a data SIM plan can be taken on pay monthly SIM only contracts starting from one month's duration.

Again, the better deals are available on lengthier contracts, but if customers don't want to be locked in, rolling contracts are available.

The amount of data available with SIM only contract deals varies from 500MB up to 50GB or more. This represents a practically unlimited data SIM only deal, depending on a customer's usage.

With any data SIM plan, however, customers should genuinely assess their usage before taking any deal with a high level of inclusive data.

Remember that a pay monthly SIM on a rolling contract can be cancelled at any time, meaning a customer could increase their data allowance if they find they're exceeding it by switching to another data SIM plan.

Customers can switch networks and keep their number. This is still the case if they're switching to a SIM only contract.

All customers need to do is obtain a PAC (Porting Authorisation Code) from their existing provider, which they must provide by law within two hours. To obtain this code, customers should contact their current provider's customer service team.

In line with customer fraud prevention, callers will be asked to identify themselves via the details associated with the existing account, so customers should make sure they have everything on hand when they make the call.

A PAC lasts for 30 days from the point of request. If it isn't utilised within that time frame, it will expire and a new one must be requested.

Once the PAC has been obtained, customers simply contact their new provider to supply the code and they can start the process of switching the number over.

If an order is made online, however, the process is slightly different, although customers will still need to obtain their PAC ahead of switching.

New SIMs will be supplied with a temporary number and customers will need to contact their new provider with details of the temporary number and the existing number that they want to keep, along with the PAC provided by the previous network.

Usually, the existing number will be transferred to the new SIM card within a few working days. It may even be as rapidly as the next working day.

If a customer is swapping to a new tariff on the same network, the process is generally much easier. A provider's customer service helpline should be able to enable a simple number switch within the same network.