All government websites, that do accept CC for Fee payments generally charge a surcharge of 2-3% inclusive of GST. In your case, 105 as fee is not justified. You should cross check with the bank for the same, however, they'll have the argument that while you were inserting the OTP, you would have seen the amount, and that is what go debitted. Then, they'll pt the blame onto the Payment Gateway.
You can try and check if you can find what led to the extra charge.