I checked some of the prices and they're indeed cheap, but the 15-minute expiration window is a bit too low [you'll have more customers if you could offer those for a longer period].
It was a bit weird that the only way to top-up an account, is through a third-party website that could "only" offer a set of predefined amounts [you might want to reconsider that part].
The 15 minute time period should not really matter as they are usually used as soon as you need verification and if the number isnt being used or you just dont need it then you can refund it within 2 minutes of purchasing instantly right from the panel and get another one if needed.
Also about the way we process payments, I'm currently in the process of configuring my own crypto pay server so I dont need to go through using shoppy since a lot of people just message me to buy custom amounts.
