Frustrating experience with repair... Am I stuck?

Where should I start...

I purchased a new iPhone X two weeks ago... My biggest mistake started from there... Because I wanted to save a few (well, actually quite a few) bucks on sales tax, I ended up with buying from a vendor I later identified as a non-authorized dealer.

It was a brand new phone, but I found these...

Maybe my second mistake was there... I didn't immediately contact the vendor; instead, think I thought this phone is already mine, I contacted Apple for a repair.

I clearly noted that "near the mute button and the volume button on the metal frame there are two spots of unevenness and sharpness". Upon sending my phone to repair I also attached a sticky note with two arrows on it showing exactly where the two spots are.

A few days later I received my repaired phone and on the repair report they say:

"They have successfully repaired your iPhone by replacing the following parts:

... Camera...

... Battery...

... Display...

... Side Button Flex...

... MLB... Symptom: No Power/Wired Charging Issues"

And due to the replacement of the MLB, I got a new serial number; and the phone's model changed from MQA82LL/A to NQCN2LL/A. Now everyone knows this phone is an replacement phone.

But the dents on the frame are still there.

So clearly, they replaced every functioning part of the phone, and just left the defect part there.

I reached out to Apple. And after a 2-hour long marathon of conversations online and over the phone, I got the following response:

They didn't replace the frame because the dents are cosmetic imperfections and are not covered under warranty.

And I told the customer relations specialist that the dents are sharp and can scratch the skin on my fingers whenever I operate the buttons. Response: if the dents are protruding, then this is not cosmetic imperfection but instead damage. The damage is not covered under warranty and will cost $549 because I don't have Apple Care.

Okay. But I said, it's a brand new phone! It shouldn't be having the obvious defect which affects proper use.

They said, then I should go back to the vendor and discuss what can be done, but Apple can't intervene because it's not an authorized dealer.

But I said: How can a vendor, even not an authorized dealer, take back a phone with a different serial number? They sold me a MQA82LL/A, and if I were them, I wouldn't take back a NQCN2LL/A, either.

But the change of serial number and model number is due to the replacement of the logic board... I never asked them to replace the board! The replaced board, and hence the new serial number and model number, made me ineligible for returns, replacements, or any coverage of credit cards, as far as I'm concerned.

I think I'm totally screwed up. Spend $1000+ on a new phone, haven't used it for a day, and end up with it disassembled, good parts replaced, bad parts still there...

What a lesson learned...