I dont know what bank yours was but Barclays tried the same thing with me. Tell them to go stuff themselves or, better still, do what I did and demand to see the Manager - S/He will have set the little scroat who dealt with you targets for opening accounts, selling insurance, loans, etc etc - They dont care what they do to sell them and will lie if they believe they can get away with it.
They will back down, then close your account and stuff them. I know its not nice but it makes you feel Soooooooo Good !