Urban Company — Broke my ac part

I took ac service and gas filling service from urban company on 24 may 2020. The technician did the work and left. The very next day, some unusual noise started and i called the technician again, he checked and removed a small piece of thermocol, said this was making noise. After few hours the unusual noise started again, i called him again the next day and then he opened the ac and said during servicing some part didn’t attach properly now i have fixed it. Then the noise disappeared. But after about 2 months and few days, the ac cooling started reducing drastically and i wrote a complaint to urban company, they sent the technician, he checked and said that he did not tighten a nut from where he filled the gas therefore the ac gas leaked. He refilled the gas and tightened the nut. My father asked him to check the coil as well which he welded but he refused to do so as it was a little more time consuming. And after one month that is on[protected] my ac broke down again and it’s not cooling at all, i suspect a gas leak problem. Gas is for around 2800 rs and i cannot keep paying every 3 months. Either the technician is using sub standard quality material or he did not weld properly so that they can ment money from us. I wrote to urban clap on 18/09/2020 and they called me today i. E. 19/2/2020 and they said you will have to pay for the gas again.
I want to request you to pls help and take action against them.
Thank you very much