Organization of donations/project support via SMS, for individuals in small sizes?

Question

Donations

From a series, a service that has its own number and the ability to forward prefixes.
So that a user who wants to help, but has only a phone, can send an SMS to a number, for example "12345" with the text "FUND SUCH 15", with the last digit in the requested amount. Suitable and just a fixed price.
The problem is that almost all services either charge an extortionate percentage or require a huge contribution that is inappropriate for the idea.
I'm already thinking of giving up on this idea.

Answer 1

Commissions when paying from a mobile account are always high. Everywhere.

Answer 2

maybe with a blog with google ads?
write about the stages of a long journey, attract potential users and philanthropists