Cancelling a mobile contract can be a tricky business. Mobile phone providers go through a lot to get and keep your business, including subsidising phones, offering promotional deals that cost them money up front, and incurring hefty advertising costs. It is no surprise that they therefore charge stiff penalties in the form of early termination fees (ETFs) if you want to get out of your mobile contract early. There are, however, some ways by which you can attempt to get free of your mobile contract in the UK without running up an even larger bill.
Check with your mobile phone service provider to find out its ETF amount. This rate varies by provider, and providers frequently adjust these rates in ways that are unfavourable to anyone seeking to terminate their contract early. If that amount is acceptable to you, you can stop here.
Read over your most recent bills as well as any communications you have received from your mobile phone service provider. Make note of anything that has changed between bills, even if it is only a 5-p fee increase. Such changes may qualify as a "material adverse change of contract." Most mobile phone service providers will allow customers to end their contract with that provider with no ETF if they have a reasonable claim of "material adverse change of contract." If you do not spot something of this nature, you will most likely have to pay an ETF to cancel. If you have spotted something you think may qualify, proceed to Step 3.
Call your mobile phone provider and ask to speak to a manager. You will not be able to get the service you require from the first level of customer service. If the first level of customer service is insistent that you explain, describe your situation in detail and politely but firmly insist on talking to a manager.
Explain to the manager that you believe you have a "material adverse change of contract" situation, and give them details as to what you believe is the problem and when and how it occurred. If she agrees, she will allow you to cancel your contract with no ETF, but you have to be able to provide ample evidence in order to back your claim.
Call as soon as possible to cancel your contract after you notice a potential "material adverse change of contract" item. Most such situations have very limited periods of time in which you can act and hope to receive a favourable outcome.