Customer Reviewsfor509 Construction

I used thumbtack to choose a construction company to do some work at my home. I chose 509 Construction as the reviews were good.
The staff member, Grant, came out and went over all the work I wanted done. One of the many jobs was to remodel the bathroom. Esthetically, The work done/looks fantastic; however, but a few weeks after construction was completed, issues became apparent in the master bathroom. As I turned on the water in the sink, I could hear water sounds gurgling in the tub. When I took a shower, the toilet water would begin bubbling and/or would disappear or start filling up. Sometimes, I could hear water noises in the tub as if something was leaking. In addition, the next time I took a longer shower, the shower water did not drain.
I called Grant and he did not answer so I sent him a text message. He did not respond nor did he call me back at first, but eventually, this guy who was super friendly when he was in my home, told me to contact the company which I did. 509 has given me the run around sending plumber after plumber and after 2 months of complaining and emails back and forth I am unable to use the bathroom I spent over 20k to get remodeled. In addition, I asked multiple times about a permit # and if an inspection was done. After multiple emails I finally found out a permit was never done. When I initially asked Grant about a permit, he stated it would be covered by 509 since it was a minor expense. I believed Grant because I felt he was honest and seemed very eager to do a good job in my home.
So many plumbers have come to my home supposedly to see what the problem is. Most plumbers have stated multiple issues and when I asked for something in writing, I again get excuse after excuse. Because I didn't know who or what to believe, again I have insisted on an inspection. I was told by John that he would take the lead on this and assured me everything would be done.
I did not want to file a complaint but to date, I am paranoid to flush the toilets for fear of an overflow, I take quick showers because they get clogged. I cannot use the tubs at all and if I run the water in the sink, the toilet water either starts bubbling, begins to fill up or completely disappears.
All I am requesting is the work in the bathroom to be done correctly, a permit be completed and for an inspection to be done so I can be assured everything is working. After paying over 20k for the construction I don't believe my request is unreasonable.