Absolutely. Mechanics like working for free, as I'm sure you do. Try getting a refund from a doctor when they don't cure you on the first visit. For some reason, mechanics are held to higher standards than doctors.
The other problem is supplying your own parts. I understand the reason, which is to save money, but that's like bringing your own food to a restaurant and asking them to cook it for you. When the shop supplies the parts, at a small markup, they assume the responsibility if they prove to be defective. When you provide the parts, the shop can legitimately charge you again to replace them the second time. The parts markup they charge goes, in part, to cover the mechanic's labor when he has to do a job over again when it wasn't his fault.
You didn't say what was wrong with the original differential or why it needed to be replaced, so at this point I can only offer that there are different gear ratios available, and you have to find a replacement differential with the same ratio as the rear unit. Assuming you did that, we would need to analyze the original failure, which isn't common at the mileage you listed, to figure out if something is causing it. One thing to consider is if there's a tire on the vehicle that's has a different outer circumference than the rest. That will put a lot of stress on the transfer case, but only when it's in four-wheel-drive.
Monday, November 19th, 2018 AT 7:29 PM