Another mind blow surprise fro TCS

My hr told me to complete the notice period of 90 days before leaving. I have been on the bench for the last 20 days so I prepared and got one job.They want me to join within 45 days.

Now my hr wants me to join a project based on skill and I want to leave because I am getting high pay there.

In brief discussion they told me you have to serve notice period here till then give training to two members of a project.

What should I need to do to get my experience letter. I have good skills in UI UX Designing.

If I serve the notice period here then definitely I will lose my offer.