Water in the Fuel Tank

We took our truck in because water got into our gas tank. He drained the water and cleaned the fuel injectors (without informing us or getting the go ahead from us) and charged us $830. The next time it rained we got water in our gas tank again, took it back to him and this time he said well the fuel injectors must need to be replaced so he replaced all of them and drained the tank and drove our truck 40 miles (why? I’m not sure). Charged us $1000!!! The next time it rained we got gas in the tank again! We took it back to him told he that he needs to figure it out and fix it for us free of charge. He just scratched his head and said; maybe someone is putting water in your fuel tank (Really? Every time it rains? Com’on!). After he drained and gave us an unauthorized oil change and told us he couldn’t figure it out he charged us $185 and wouldn’t give us our keys until we paid. We paid him over $2000 (not to mention 3 towing fees) and the issue still had not been fixed. We then took it over to a friend of my dad’s that tinker’s on cars (not a licensed mechanic) his first thought was to take the bed of the truck off and see if there were any rust spots on the fuel tank where water could be getting in. Lo and behold when they did that they found it and were able to fix it. Why on earth couldn’t this guy do that? His best thought was, someone was putting water in our gas tank. I would never, ever take another vehicle back to this guy. He obviously does not know what he is doing.