Hi, These over the phone contract "renewals" are subject to the same scrutiny that sales agents for power companies are. I.e. they need to prove (through the use of a call recording) that you consented to the extension having full knowledge of the extension.
They tried it on with me, offering me a £2 a month "discount" on my BBand. At no point did they tell me that it would be a contract extension, however i figured as much anyway. I said no explicitly, and a couple of months later received an email to say that my contract had been renewed.
When i phoned up I stated that I had never agreed to an extension. The response i got actually made my jaw drop. They said the computer screen stated that i had consented.
Basically, i just politely responded that at no point had i agreed to an extension. The onus was on them to prove that i had. Failure by them to produce a recording of me actually consenting, which they didn't have as i didn't consent, would result in the contract being null and void. If they did not agree to this course of action and immediately cancel my extension within the complaints period allowed, i'd be happy to take the complaint to the Ombudsman.
Funnily enough they agreed and cancelled there and then.