Releiving letter and experience letter related

Sir I worked in a CBSE School in Trivandrum Kerala. I joined on 2022 Feb as a cashier for fee collection. After 2 weeks they asked me to sign a contract for 2 years and submit my original certificates. I refused. Further i found some discrepancy in fee section and i reported to admin officer. Thereafter i faced different issues they shifted me from fee section and for days i was wandering in the school without a seat. Then Admin asstnt resigned i was asked to do her job but they did nt give the post did all works given there. Then I was requested to move back to the fee section and i hesitated. Then i requested for a 3 weeks leave for visa renewal and they granted me leave. 2 days before coming back i informed the PA to Principal that i wil be back to duty on so date. I went bak to school staff asked me to meet Principal and Secretary met both and they askd me whethr there is vacancy. After one week they started making issue that i did not submit rejoining letter. Then they askd me sign th contract and submit certificates and they will put me bak to office. Which was not acceptable to me and i submitted my resignation. I was not given any PF or ESI provision till date. Now they are not ready to give me exp certificate.