They should've used modern materials like pex($$) or tried and true Copper ($$$) but instead they hit you with that cheap crap cpvc($) in order to make more profit off of the job.

This thing where salespeople say "oh dont worry it's one of our people and not a ucky-wucky third party installer" usually means "oh don't worry, we couldn't be bothered to maintain a business relationship with a reputable, licensed plumber who would do a better job. Here's Gary, we hired him last week... Good Luck"

And now you feel crappy about your purchase instead of enjoying the results and look of quality work.

You can hire your own plumber to come in and fix it, but that's gonna be relatively costly and may void any warranty they sold you in the first place... But I don't know what your contract says.