Midtrans does refunds for free but the initial transaction charge cannot be returned.
For example, if a customer pays IDR 100.000,- and requests a refund, the customer will receive exact IDR 100.000,-
The merchant will receive IDR 94.300,- and will need to return the full IDR 100.000,- to the customer. Midtrans will ony return the MDR fee (IDR 3.200,- in this case). So, merchant incurs a net loss of the processing fee (IDR 2.500,-)