Cred — Refund of late fee charges

Hi, I had paid my credit card bill through CRED. I had paid way before my payment due date of credit card. Now CRED kept my money for 10 days and after that it refunded me my money saying my payment has not been processed while it was when I had paid. Now my credit card payment date had passed so my credit card company imposed a late fee charges of about 1200INR. I contacted CRED about this, firstly they denied to help me. Then I convinced them that its their fault so they said they will pay me. It has been more than a week I have been mailing them daily but they are not replying nor they are giving my refund. I had sent all the evidences proofs to them too. Please help.