pressure due to changing the hoses doesn't sound reasonable. Hopefully some of the more experienced members here can help you out. Either way, arm yourself well with information before making any accusations. A place like that wouldn't feed you a BS story if there was any chance of being caught because that's terrible for business.
Your best bet is to have someone you trust take a few minutes to look at it and give you a second opinion before investing a bunch of money. Good luck -Eric