Barclays Bank — Amount is paid but now received NOC letter

Hello!
I got a call that to pay may credit card outstanding amount after I cleared everything before 5 yrs. Now I got a call to pay the amount other wise there will be forwarded that to the court and I have to pay the amount 10 times with the penalty.
So to avoid huge amount I had paid the outstanding amount. But still now I didn't receive any NOC or NDC letter. I am calling to the agent who raised the complete, but he is not lifting my call. So how should I know that wheather I have done correct payment or not?
Sir please help me I have paid a huge amount. Hope I get a reply as fast as possible.
Thank you