Both the SMS Wallet and the AI Wallet apply a 3.5% processing fee at checkout on a manual purchase, stated on the wallet pages ("A 3.5% processing fee applies at checkout"). Selecting $100 of SMS credit therefore charges $103.50 to your card, while exactly $100 is added to your balance. The fee covers the card processing cost of the top-up; it is not deducted from your credits.

For automatic refills this only fully holds true on the SMS Wallet - its auto top-up also charges the refill amount plus the 3.5% fee. In the current version, the AI Wallet's automatic refill charges only the plain refill amount with no fee added, unlike a manual AI credit purchase.