Plumbing Issue with plumber threating

[Sam Abe]

I own a property in Los Angeles which has had plumbing issue with water flowing back from the toilets and this issue has been going on occasionally since last year. I spent 7000$ initially to change the plumbing line from yard to the street line with a plumber last year. Then this plumbing issue still happened again so I hired some one else who promised me that he knows the issue is lack of slope and can changethe remainder of the pipe for another 4000$. He did the work a few weeks ago and the problem still continues. I havent paid him because right before paying him this happened again where the toilets flood and get the carpet damaged etc with sewer water which itlsef is expensive to address.  Now he is hassling me for payment and telling me he will pull the permits tomorrow and get an inspector though the work is already done few weeks (not correctly ofcourse as the problem is still existing) and he is telling me if he did that he will get me in more trouble as there are unpermitted gaslines which I am not aware of as I just bought the property as is and havent made any changes. He is telling me if I dont pay him he will get me in trouble with the city by going and pulling a permit tomorrow.  I didnt sign any contract with him. He claims he is licensed. I hired him because of refeerral and now he says he couldnt slope it becuse that was not possible but has changed the line and I owe him money where as my pipe is still backing up every time we flush.