SIM only deals are excellent for cutting down your monthly outgoings because they're normally slightly cheaper than standard monthly contracts.
They're also great if you're happy with the phone you've already got. It means you can change the benefits of your network, or have more flexibility to change networks.
If you're waiting for a specific phone, but it's not on sale just yet, SIM only is brilliant. Because of the short contracts, you can end your contract and get the phone of your dreams whenever it launches.
There are three different SIM types. You'll need to get the correct SIM for your phone, or it won't fit in the phone's SIM card slot.
A nano SIM is the smallest SIM card and is used in phones like iPhone 5s, 5c and 5, HTC One (M8) and the Nokia Lumia 1520.
This is the second smallest SIM, and is the most common one used in smartphones. iPhone 4 and 4S, Sony Xperia™ Z1, Samsung Galaxy S5 and S4 all use this size.
Another very common SIM size that's used in lots of older smartphones and most feature phones like the Samsung Galaxy Ace, Nokia Asha phones and older BlackBerry phones.
This is the same as a standard SIM but gives older BlackBerry® devices access to BlackBerry services. This is not needed for new BlackBerry phones running BlackBerry 10 OS such as the BlackBerry® Q10.
You'll need a PAC (Porting Authorisation Code). This is a code that lets you transfer your current number to your new SIM card. It's free, just contact your current network.
Use your PAC in the basket page. You'll see a section called 'Keep your number'.
If you're getting a Talkmobile contract, you have to fill in this part of the page during the checkout, or your number will be lost. All other networks can swap your number over after your phone has arrived, but it's a good idea to do it when you buy your SIM.
A 30 day SIM only deal is very flexible, letting you cancel and start a new deal practically whenever you want. If there's a phone you're waiting for and it'll be on sale in only a few weeks, a short 30 day SIM only deal is ideal.
A 12 month contract is still more flexible than a two year contract, and offers better value than a 30 day contract. You get a bit more for your cash, helping you save money.
An upgrade deal means you buy a new deal on your current network to replace your old deal. Often you'll get a better deal by upgrading.
The fastest way to check if you can upgrade right now is with our Upgrade Checker. Just fill in your details and it'll let you know straight away whether you can upgrade today.
Whether you can actually upgrade or not depends on how long you've had your current deal. The length of time varies from network to network, and whether you're on pay as you go or pay monthly. Have a look at our upgrade help page to find out more.
Most of the phones sold at Carphone Warehouse can be used on any network. If you have a phone from someone else though, you might find that SIMs from some networks don't work in your phone. It's very easy to fix. Just call up your current network and they'll unlock it to all networks over the phone. You might have to pay a small fee though. You can find out more here.
Some tablets can connect to the internet in the same way as smartphones do using network reception. These are sometimes called connected tablets. We sell special SIM only deals that include a set amount of data each month. Slot these SIMs into your connected tablet and you can get online anywhere.
A Shockproof plan on the iD network gives you control over your monthly bill. Every plan comes with a £5 'cap' on your calls, texts and data, so you'll never be able to go over your limit by more than you can afford. You can then easily view how much you've used at any time of the month, by logging in to your account. So rather than feeling shocked each month, you'll feel in control.