When you phone them and get the options, just go stright to the cancellations department straight away and bypass the middleman.
Funny how when you want to speak to them about leaving you are guaranteed and English (or at least Welsh) voice on the phone.
Mind you, I'm pretty sure that if you got through to the Indian call centre and said "I want to cancel my contract because my bill is too high", their response would be "I am very sorry to hear that, have you tried re-booting your pc, oh your bill is still too high, you must turn off your modem, oh your bill is still too high, well obviously there is no problem then".