Company harassing and sending legal notice what can be done

Hi, I was working with an IT firm in indore, I met with an accident because of mental stress and my company pressurized me to resigned I resigned, After 3 months i have received a call that still want to continue with me and I have joined them back without signing any rejoining bond. still they continue to harass me long working hrs, no salary at time I said i cannot continue I resigned they have kept my security check of 18000 and pressurizing me to pay, as i was in Probationary period I left , They have sent me a legal notice of check bounce. Please suggest me a solution