Is it permissible to send an amount in US dollars via a Visa card to a study website that deals in Swiss francs, through an electronic link, given the difference in currencies and not knowing the exact time of receipt, and does this fall under the ruling of riba al-nasi’a (usury of delay)?

It is permissible to transfer the amount using an electronic card via a transfer link, even if the currency differs. The currency exchange takes place between you and the bank, and constructive possession occurs therein. Among the forms of constructive possession considered valid in Sharia are: the bank entry of a sum of money into the customer's account, such as direct deposit or bank transfer, and the immediate currency exchange contract between the customer and the bank, or deducting an amount from the customer's account to another account in a different currency. Delay in bank entry for customary periods is overlooked, provided that the beneficiary does not dispose of the currency during this period except after actual receipt is possible.