Urban Company — The issue is not fixed, not desired output and the charges are very high

I had booked for waterproofing wall portions on 26th Oct 2023, the guy did not do a proper job.. he left by evevning telling everything will be fine. Unfortunately I wasnt home and only my wife was there. By night when I came back from office brown patches started showing up. For that pathetic job they charged 21k. After coming home I realised the materials they purchased was only for 1000 Rs. Because I was getting frequent calls from UC to make the payment I paid through gpay from office. Now they are saying I have accepted the quote and made payment, so it was my fault. They are not revising the charges and when contacted I have to always wait for the support to come online and say someone will come. Since morning thrice they told me that someone will come but no one turned up. I request a refund / fair price for whatever rubbish work they have done. It is not even worth 3k and for this they have charged 21k.