This one just made me laugh. Am I wrong?

Electrician by trade. We do a lot of work for a company that strictly do high end bathroom Reno’s. With a lot of heated flooring. 90% of the time it’s adding can lights exhaust fans etc. and running a home run or 2 for the floor thermostat/power module depending on the size of the floor. We end up having to make 2 more separate trips because after we finished the floor wasn’t heating properly after a few hours. We go back, troubleshoot and find out the GC bought the wrong thermostat. Gets the right one so we have to make another trip to install. No big deal, shit happens I get it. Here’s where my gripe is - for some reason this particular GC always wants me to bill customer direct, which is fine. On this job customer calls about the invoice seeming high, and I tell them that’s because we had to make 2 extra trips due to the equipment being wrong. Then the GC calls me butt hurt because the homeowner is mad about the price and says I threw them under the bus. All I did was tell the customer why they were being charged what they were. IMO he should have covered the 2 extra trip charges and I would have given the homeowner the original invoice. What do y’all think? Am I in the wrong here?