This happened to me last week.In my case,the caller said my bank was not accepting the card I tried to pay the supposedly unpaid bill with with and suggested I fetch a neighbour to pay it with a valid card.It was only when the greedy would be thief rejected my neighbour's credit cards too that we realised we were victims of a hoax. The telephone company assured me my bill was paid and the police are now investigating.
Fortunately I was able to cancel my card before any damage was done as did my neighbour.
I don't usually share personal stuff, but I want to warn everyone to be on their guard. I always thought this sort of thing was just something that one read about, and was maybe an urban myth,but sadly it is not.