On top of Coinmama's fee and the credit/debit card processing fee, the final amount may still be larger than expected. When this happens, it is most likely a Cash Advance Fee; a fee levied by your bank or card issuer for making what they decide is a cash transaction. We have no control over this and can not see it anywhere on our end.
We would advise you to contact your bank and dispute this fee. Make sure that you do not dispute the entire transaction, or you may accidentally file a payment dispute which could end up hurting your credit rating, among other things.