As of 1st October 2018, if you switch providers, renew your contract or enter into a new contract with your current provider, you can request a bill limit. This will be included in your contract.
You can choose the limit to set, depending on your needs. For example, you can set a ‘£0’ limit if you just want to pay your contract price and want to stop using your mobile services as soon as you reach your monthly allowance. Or you could set a limit for a little extra above your contract price