Refund related query ...

Hello everyone,
Need urgent answers plzz,

my client has wrongly paid tax in igst in one month and next month to correct the same , paid tax in correct head ie cgst sgst ... each amount above mentioned is paid through credit ledger...

now i have applied refund for same in cash but department gave notice and mentioned that u cant take cash refund because u paid excess through credit ledger ...

what can i do now ??