Although more people are signing up to mobile phone contracts, pay-as-you-go (PAYG) subscriptions are still popular.
A PAYG deal means you only pay for the calls and texts you use. You can also change or end your deal at any time.
These deals can be flexible and convenient, particularly for people who only use their phone occasionally.
For example, you might keep a PAYG mobile in your car in case of a breakdown, or give it to an older relative or a child so they can get in touch in an emergency.
But if you don't use your PAYG phone at least once every few months, when you do try to use it you could be left without a signal.
That's because if a PAYG phone number is not being used, the mobile operator can suspend the service and recycle the number. This is to ensure that the numbers they have are being used efficiently.
The length of time before a mobile provider deems a phone inactive varies: for some providers it can be as little as 70 days, while others wait six months or longer.
If you're concerned that your PAYG phone might be suspended because you don't use it enough, ask your provider: