HSBC Credit Card — credit card cancellation without information

I am Rajeev Kumar using hsbc credit card since last 6-8 months. I used the card and cleared all the debts last month. I have prrof of the same as I have done it online. The main problem is that even after using the card properly and paying all the debts on time my card has been cancelled by the bank. And to my ashtonishment customer care has no clue why has it been done and also collection department says that they also dont know anything so talk to customer care. When I went to a merchandise to use the card the machine said that it is a pick up card. It ruined my reputation in front of the shop owner who blankly looked at me like I am a thief.

I just seek help from you in solving this because every time they say contact CC and CC says to contact collection department. What should I do in this case? Should I also sue them for my problems and my loss of rapo infront of the shopkeeper?

please help me I am available on mails and phone any time.