Employer ignored the Appointment Letter

After 10 years of serving, I resigned from my old organization on 9th March, 2021. As I had to join a new organization on 22nd March, 2021, I was not able to serve the notice period (1 month). According to the clause mentioned in appointment letter from old employer, I was ready to pay an equivalent amount of my one month salary. Since I was very helpless, the employer took advantage of this, ignored the appointment letter and forced me to pay 3 month salary. They were not ready to relieve me without three month salary. As I was helpless, I paid them my three month salary because without getting reliving letter from old employer, new employer was not ready to give me joining. Moreover, if I would not have paid them 3 month salary then they would not provide me the experience certificate, Relieving Certificate and my gratuity amount. As per appointment letter, they took 3 month salary which is clearly wrong. Is there any way, to recover my 2 month salary from the old employee? What can I do?