What is the ruling on taking a transfer fee in exchange for giving a sum of money here and informing that its equivalent has been transferred to another country?

This transaction is permissible provided that actual possession occurs in the exchange. If actual possession does not occur with deferment, then it is not permissible.

Actual possession can be nominal (or constructive) via telephone, where a person abroad receives money from their associate and, at the same time, contacts their agent in the other country to give the amount in the other currency to their relative.

If the transaction adheres to these conditions, then charging a fee for the transfer is permissible.