Is it permissible to purchase for customers from foreign websites using a prepaid visa card in euros, then collect the value of the purchases in dinars at the euro exchange rate of an electronic bank, which differs from the exchange rate of physical euros, and profit from the difference in price? And is it permissible to deal with shop owners to attract customers for a commission?

Purchasing a visa for clients falls into two scenarios:

The first scenario: You purchase it with your own money, then demand the money from the client. This is considered a loan, and any increase over the amount paid is impermissible because it is usury (riba).

The second scenario: You take the money from the client, then purchase it for them. This is a permissible agency (wakala). However, if a fee, commission, or any profit is taken, it is a condition that the principal (client) be aware of it, as profit without their knowledge is not permissible.