Hello - I'm having an issue with my regular mechanic I've known for about 5 years who on my airplane's last Annual (this month) replaced the ELT and on the Invoice, it shows I was charged for it - labor and parts - about $380 total. Problem is, the same mechanic replaced an expired ELT on the last annual - August 2023 - and the new ELT put in last year was listed as having a 2026 expiration date. In other words, for this Annual this year (this month), the ELT did not have to be replaced, yet that is exactly what my mechanic did. I've emailed him last year's Invoice, from August 2023, plainly showing that a new ELT was indeed installed, and that I was charged labor and parts for it. It's been a week, and he hasn't responded. Bottom line is someone's going to have to eat about $380 and I don't think it ought to be me - as I didn't make the mistake. As yet, he doesn't seem willing to face this fact. Bear in mind, of course, this is the guy I trust to take care of my airplane. I don't want to go over his head, to the owner of the FBO, and I don't want to get in a ****ing match either, with my mechanic. But neither do I want to fork out $380 for his mistake. I'm really not sure what to do, other than call the guy, or visit him in person, with last year's invoice in hand, to show him, on real paper, that he replaced an ELT that doesn't expire until 2026. I haven't as yet paid for the Annual. I'm tempted to just pay all of it, minus $380. And if the owner of the FBO questions me, I've got to then tell him, why it's $380 short. Any ideas or suggestions? Thanks!