In the US, all operators except T-Mobile allow "Send SMS to donate" both as a one time donation and in subscription mode, i.e. "donate 2$ per month".

Note in the US all carriers require campaign approval, and T-Mobile does not allow any such charity campaigns.

In other markets such as UK and Australia these programs are much simpler to implement

There are requirements such as confirming doners mailing address to receive tax credits on the donated amount for example, all easily enabled through ZOOMtxt.