Company is not willing to give reliving letter

Hi All, I have joined an IT pvt Ltd company on 3rd feb 2020, after 2 -3 months I get to know, it has toxic culture and unprofessional env. So I again started searching for a new company, but unfortunately Corona came into the picture and because of stress and tension of loosing my job, I carried on to Work. But on September 2020 , they asked me to re join the office. But I was not well and was unable to join the company. They forced me to join the office otherwise they will only pay 50%. In the mean time I got an offer from some other company. So on 6th of October 2020 I mailed the HR that I won't continue with organization as I got an offer from another company. And I am ready to pay the 3 month salary amout(written on Offer Letter that you should pay 3 month salary if you wanna leave prior to notice period). I joined the new company on 7th oct 2020 , because I wanted to leave this company as soon as possible After waiting for around 10 days they replied me and said I am doing dual employment. Also they didn't credited my September Salary. After all this I went office on 26th of October 2020 with my father and to pay buyout amount but still they clearly want me to serve 3 months notice and wanted me to work from office. And till now they have not provided me the reliving letter. Is it wrong to stop your employment from a company where you constantly feel toxic. Is this wrong that you can't bare the unprofessional behaviour. What should I do now? This is affecting my career. I want My reliving letter.