1- When I had a journeyman's card it stated I was to work under the direct EMPLOY of a licensed master plumber NO SIDE WORK.
all work was to be under the direct auspicious of a LMP
2- Why anyone would place Teflon around a flange is beyond my comprehension as there is something called plumbers putty
3- Teflon is great for male threads and rolled Teflon is great for packing glands on valves instead of graphite as graphite can score a valve stem over time and does dry out.
4- Materials supplied by others I will NOT take responsibility for ESPECIALLY if they bought it from a big box store.
I had an account who decided to buy all materials and only wanted my labor which I said no problem and I installed the faucet he supplied and as luck would have it IT LEAKED and I said OK it is defective PAY ME MY $150 and let me know when you get another faucet.
He said could I wait for him to drive to the big box store and get an exchange and I said SURE BUT your going to pay me my $150 per hr even if I sit here waiting.
He paid me and I left about an hour he called my office asking me to come and install the new faucet and it too leaks this time by the spray hose and again I was paid as it was not my fault.
Plumbers like other trades have to charge a higher price then we pay for materials because manufacturers today put of really bad imported products and the installer takes the hit when we supply a defective part as we have to eat the labor to replace it.
Now for the good news anyone doing "business" supposed to have some type of certificate of insurance to be in business and a journeyman NORMALLY cant own the business as they have to work UNDER a master plumbers license.
Technically in some states it is considered against the law for someone to pass themselves off as a "plumber" without being duly licensed.
There is also something called a mechanics lien for non payment of services rendered.
What you could do is hire a licensed Master plumber and have her or him check the job and make repairs as needed and get a written report of what they found.
Normally you take a risk suppling materials and it was a gamble and if it was a plastic waste lots of luck as you get what you paid for.
The only thing I cannot understand is the use of Teflon on the flange BUT hey they be out there