I'm betting that this rant wouldn't have happened if she had politely talked with you about the service charge instead of going off like a vial of nitro that had been sitting in the sun all day. You would've understood, and would've just paid it and moved on with your life like a reasonable person.It's not just the charge but also the attitude of the person in their front office prompting me to look at other shops.
It's usually not the problem that causes trouble, it's how the customer service reps respond to it. Maybe she was having a bad day, or maybe she's just bad at customer service, but her attitude certainly did nothing to make the situation better.