Gopal,
Were all the other transactions on the bank statement imported correctly, apart from other incoming payments?
If so check, if you have a similar code entered for credit on configuration. That's all you need to do, if it does not work you have to then log an incident with SAP, sighting all the checks you have done. As the system must be picking up the credit for the transaction code from somewhere within the system.
Regards,
Emeka