Employer Not releasing employee

Hello sir, my name is Jayashree M, I work in IT sector Altran Technology of Bengaluru Location,im facing lot of issues in workplace by my company, firstly my dedicated access to work in the company was not given and I was working with other colleagues systems from almost 1 year,still I'm continuing same, & when I'm not comfortable and resigned my job on aug 07 2019 and also requested for buyout at aug 22 for oct 07 to Nov 08, I m currently serving 2nd month notice period for 1 month I asked buyout , initially It was agreed by HR and senior manager,now at the last 2 weeks of my last working day they are creating problem to me, initially it was told as an when replacement comes in my place we will release you so that client billing shouldn't effect,I followed up with HR and senior manager & now when they have found out resource still they are not releasing me stating client is not agreeing he Wil decide whenever he feels on Oct /Nov month if he needs replacement or not & forcing me stay