The "Indian call centre" only deals with Broadband/Dialup Technical Support enquiries. They do not deal with billing in any way, shape or form. If it was definately Customer Services you called, you got someone of Eastern descent in Swansea, Manchester or Glasgow.
However, if you'd like to PM me your account number, full name and address I'll look into the billing for you. One of the CF team can confirm I'm an ntl associate, and I'd advise you await their confirmation before sending personal details to anyone.