Mobile Money Transfer
The most common fee structure is usually a one-off fee plus an exchange rate that may or may not also have a mark-up ranging between 1% - 3% above the mid-market rate.
Banks are typically still used for large money transfers due to the security and handling of the funds although there are a number of new fintech entrants that are quite capable of handling large sums of money, just be sure to check the fee structures first..
Ensure the money service provider you are using is regulated by the relevant national competent authority. In the UK this is the Financial Conduct Authority (FCA). If in Europe ensure the company follows European Payment Services Directive rules designed to protect customers who use payment services.