Understanding Notice Period Clauses
If the clause in your appointment letter states that you have to serve a mandatory 3-month notice period, then you have no option but to serve your entire notice period. However, if the clause states that either the employer or the employee can waive off the notice period and the dues shall be recovered at the time of the full and final settlement, then you can serve a 1-month notice period, pay the salary for the other 2 months, and join your new assignment.
In case you do not serve your full notice period (which is mandatory), the organization will term you as absconding, and you might lose the settlement dues that you were supposed to receive from your employer.