Sometimes, guys pay in advance or pay a deposit. This works for me, especially for new customers, but you need to show up. You can bet someone else would like to use the slot, and I depend on keeping my calendar filled.
If you can’t make a date, call at least 24 hours in advance, so I can use this time for someone or something else. If something happens at the last minute, I understand, but I won’t likely be able to get someone else to fill your slot, especially if I’ve got someone already booked after you, so I’d rather you be out than me. In this case, I might be able to reschedule and at least give you some credit, or maybe you can accept a shorter date for the amount.
If you pay a deposit or the full donation and you are a no-show without adequate notice, don’t expect a refund or a different date. I may be charitable, but that’s for me to decide.
Don’t be the guy who texts me a couple days later telling me that you already paid. I know you already paid, and you didn’t show. That’s the time you paid for. If you bought tickets to an Eagles game and couldn’t make it, you wouldn’t expect to use the tickets for another game. It’s no different.