Does the activation fee for a purchase voucher, which exceeds its nominal value, constitute usury, given that the receipt distinguishes between the value of the voucher and the activation fee?

If the card includes a financial balance, its balance takes the ruling of stored currency.

If the card is purchased with the same currency as its balance, then immediate exchange (qabd) and equality are obligatory, and any excess (tafadul) is forbidden, based on the saying of the Messenger of Allah, peace be upon him: "Gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, and salt for salt – like for like, equal for equal, hand to hand. If these types differ, then sell as you wish, provided it is hand to hand."

If the card is purchased with a currency different from the currency of its balance, there is no harm in having an excess (tafadul), based on his saying, peace be upon him: "If these types differ, then sell as you wish, provided it is hand to hand."

As for activation fees for the card, if the company pays them to another party or for a service with a specific cost, then there is no harm in paying them. Otherwise, it is a trick to exchange money of the same kind with an excess, in which case the transaction is impermissible. The ruling depends on knowing the true nature of the activation fees.