Well after realising how painfully slow the 3 network is in Central London I called up to cancel my contract. 4 times I was put through to another department until I ended up speaking to someone in the UK whose job title is presumably 'Professional Patroniser / Time Waster'. I told him I wanted to cancel my contract, he asked why, I explained my problems. Fair enough I thought - this should be over quickly.
I snipped the rest but the whole experience you describe is pretty much the same as mine and like you, I'd rather not go through that again. In my case it was for a mobile broadband and a phone account so doubly painful