Is helping people pay fees for which they do not have a credit card by paying with my own credit card, in exchange for an additional 5% of the amount paid, considered forbidden (haram) or usury (riba)?

If the questioner pays the fees with his bank card first, then takes the amount he paid in the same currency plus an increase, this combines two prohibitions: The first is that he is in the position of a lender, and it is not permissible to combine a loan with any exchange contract; because the Prophet, peace and blessings be upon him, said: "It is not lawful to have a loan and a sale." The second is that the transaction resembles currency exchange (sarf), as it is selling currency for currency of the same kind with an increase, and this is not permissible.

To correct the transaction, the owner of the transaction can pay the amount to the questioner first and authorize him to deliver the amount for a known fee, making it an agency for a fee, and this is permissible.