What should be very clear in the OP, and it isn't, is that he got the parts number, as he wanted. That should be the first sentence in the OP.
The title of the OP is misleading. It makes the reader think that the customer service didn't do their job, or they didn't help the customer.
The title should be fixed. And in the OP it should read clearly that the issue was resolved without any problems.
By the way, I know a lot of people who probably would mess up changing a pickguard. Scratches on the body, stripped wood from screwing, pulling a wire loose, etc..
This whole thread is useless.
"I was rude to someone who was likely dictating an extremely broad company policy per the requirements of their position and now I want TB to tell me that I was right to do so".