Barclay Credit Card — Bill for unused service & when asked for deactivate the service ,no response

I have a Barclay credit card. When ever I took this card they called to my mob and sale a product of Troly Bag and servises worth Rs.5000/-Which I have not received.
They told after payment you will get the product.Because of bad service I decided not to continue with that product so I called to Customer care and told to cancel the Rs 5000/- service which is a customer not received the service.But they denied. I am still paying the interest of that amount .Please help. I donot want the service itself.If I drop the check as per ther instruction before 7-4 days still it will not clear and I am penalized with Late fee and other charges.After informing to Customer care they are not responcing.at last they gave me a number of Bangalore Its only ringing and I am getting bill with penalty...Pls tel me how to go about this ...