Charged $200 to repair and it worked two days

A local repair shop replaced the screen, charging port, and put a new battery in my phone. I was told there was some water damage inside but that those components were replaced.

I used it for two days although it seemed just a little sluggish. It still preformed any thing i needed it to. I had it in a thick Life proof case with built in charging backup. I charged it twice. The third time i charged i, when i checked it later it would not come back on. I tried the hard restart no luck. The case charged but the phone is dead.

The girl at the repair shop checked it out and, said she tried replacing everything again and, it still would not come back on. Claims it may have burnt up the motherboard.

I will get the phone back today and, put it on itunes to see if i can still see inside it.

I'm out $200. for nothing. All she will do is give me $20. off if i need a future repair.

Any suggestions?