Resignation not accepted by employer

I have resigned from my job after verbal discussion with my reporting manager and he gave me a last working date. First I submitted resignation in company app and after request from reporting manager submitted resignation over mail. As per my appointment letter below is the Notice of Termination : During the period of probation, your employment can be terminated without any notice or assigning any reasons thereof on either side. On confirmation, your employment can be terminated by three months' notice or pay in lieu thereof on either side. Please also note however, that the actual date of release will be at the discretion of the Management in the event of your seeking separation. According to the LWD given by my manager I was serving 22 days of notice so I also accepted the pay in lieu there of for notice period not served. Now the HR and superior managers are not accepting this and asking me to serve total 90 days and if I do not they will not release me and also has not accepted my resignation. After presarition from HR and superiors my reporting manager backed out saying that I alone cannot take the decision. I am working in this organisation for the past 6 years even I have requested that I have given six years of my life to the company pls accept the 68 days of notice not serving and I will pay in lieu there of, but the HR and superiors are not agreeing and asking me to serve total 90 days of notice period. Pls suggest a way out to get my resignation acceptance and reliving letter.