Hammer I get customers like that try to tell how to fix the machine or engine. I just look at them and "So why are you here if you know what needs to done?". I even got rid one customer this year that was insisting it only took 30 minutes to remove, repair, and re-install a Kohler horizontal engine on a Cub Cadet shaft drive mower. It took me nearly 2 hrs of fighting rusted bolts to get the job done. He came back in whining about the bill. So I reworked the bill and charged for the parts and told him to hit the road and don't come back. Then he tried making out he was just kidding around. No difference the insult was done.
I understand it can be a pain to do warranty work if you are dealer as the OEM are nitpickers. So I have never sign up to be a warranty center until last month as it was the only way to get my HG parts and transaxles warranteed. Since HG will not send a copy of the warranty policy I will bill the customer upfront and refund them when I get refunded.