What is the ruling on dealing with the British "Wise" bank, which charges a commission on currency exchange and whose contract includes a clause obligating the client to immediately settle a negative balance, along with bearing the collection costs?

If a customer purchases an item using a currency different from their account currency, the bank performs an exchange between the two currencies. It is not a condition that the exchange rate be at the market price; rather, it is based on mutual consent, with the condition of actual or constructive possession. The bank exchanges the currency for the customer and then delivers it to the seller, and it is permissible for the bank to take a commission for the agency. As for a negative balance, it means that the customer is indebted to the bank, and the bank is permitted to take the costs of debt collection, such as lawyer's fees and litigation expenses. However, it is not permissible for the bank to impose a penalty for late payment. Therefore, if the bank only takes what it incurred in collecting the debt, there is no harm.