If your pool service requires you to pay in full up front for repairs, I’d hire someone else. I can see a partial payment on some bigger repairs, because not all customers will pay what they owe. But for most things that are smaller, you should pay after the repair is done or they’ve shown up consistently for the service. If they charge you without your authorization for anything, even if it’s small, I’d let them go and not pay them another dime. That is a complete lack of integrity unless you have developed a close enough relationship and have okayed a set amount beforehand.