Is the monthly amount deducted from the client and collected by the bank in exchange for installments considered usury, and does the seller bear a sin for it?

Banking transactions to ensure installment payments are divided into two categories:

1. Bank Guarantee: If the bank guarantees the client's liability, it is not permissible for the bank to charge a fee for this guarantee, because it becomes a loan that brings benefit, which is usury (riba). 2. Bank Agency: If the bank is merely an agent for collecting the installment, there is no harm in that, provided that the seller pays the fee to the bank, because the seller is the beneficiary of the agency service.