In order to add and Role back credit from clients account you can follow given steps;
1. Login in to your re-seller account.
2. Click on administration.
3. Search the username.
4. Click on SMS Credits.
5. Click on Add More Credits.
6. Message Channel : (Promotion or Transaction).
7. Type the Payment Reference (Cheque, Cash or NEFT).
8. Add the Credit.
9. Note: To minus the credit apply (-minus symbol) before the value e.g. (-100).