dont want to cancel contract

Yesterday i phoned about 9 times. 6 of those times i was cut off before speaking to a consultant and the other three times i managed to speak to someone but every time was transferred to a dead line. I requested about 2 months ago for cancellation of contract and to go over to prepaid. they confirmed via telephone that that it will automatically just go over to prepaid but with 2 months later, no luck and still on contract. and its seems that the cancellations dept is unreachable now after all my attempts to get hold of them. please help