1. If you have resigned according to employment contract then employer has no reason to withhold your experience letter.
2. Visit the company personally and try to solve the matter amicably.
3. If they still do not issue experience letter, speak with current employer to waive off requirement of experience letter.
4. Send them a legal notice drafted by a lawyer.
5. As a last resort file case in labour court.
For further consultation please write to me at email@example.com
Sir, I'll provide you certain legal suggestions, but for that i need to ask certain questions from you. For any further assistance, feel free to contact me on my e-mail "firstname.lastname@example.org"
Shubham Pabbi & Associates
Please reach me at 9794148274