Is buying dollars with credit, then converting them into Libyana credit, considered a usurious transaction, and is immediate possession required when converting dollars to credit and vice-versa?

If the term "balance" refers to a phone balance, then compensating for it is the sale of a usufruct and is not subject to usury. If it refers to transferring money from one bank account to another, this is a pure agency. If it involves currency exchange, then the transaction includes both currency exchange and agency. The delay in the recipient seeing the transfer message does not affect its validity. A delay in bank crediting for natural reasons is excused and does not affect the validity of the transaction if the beneficiary can actually receive the funds and does not dispose of the currency during the excused period until after the bank credit takes effect.