I say, and with God's success: If the service fees set by the bank are within the usual custom for the service, then they are permissible; because there must be expenses for the employees in the lending fund, and these are borne by the clients to keep the work going. Such fees are usually very small, and do not typically exceed one percent. As for what you mentioned, four percent, this is very high, and it is considered usurious interest when compared to the usual interest rates of usurious banks, so it cannot be deemed permissible; because it is usury. And God knows best.