Resignation and Experience letter

Hi, I had been working in a company for almost 2 years. I resigned by e-mail on February 19th to my manager stating personal reasons. Again sent a mail with more elaborate reasons to my HR on February 22nd. The HR reverted that the resignation will not be accepted as I had been given an appraisal just 5 months before and was required to stay for a year after acceptance of appraisal. But this was not mentioned to me during the appraisal nor have i agreed to it. I got a job offer during the beginning of April. I again sent a resignation stating this and requested immediate relieving as I had completed the notice period of 2 months (also considering that I had a paid leave balance of 13 days, this would be lesser than 2 months). I have joined the new company. Is there any way I can get my old employer to give me some form of proof that I have served there for these 2 years. Their refusal to accept my resignation and not providing a valid reason has left me with no proof of 2 years served, as I don't have my last 2 month payslips also. Would bank transfer of salary act as proof? Can they legally move against me for leaving without a relieving letter?