what are the consequences if security cheque bounces

Hello sir, I have recently joined a company in mohali. They took my sign on a simple A4 sheet in which it was written that I am joining this company and giving them a security cheque, if i quit the job before 12 months then they will withdraw 50,000/- rupees from my account. But its 2 months i m working with them and i m not confortable with the nature of the company. They did not gave me any I card and not any appointment letter. The appointment letter is still not signed by director. The paper I signed was simple A4 sheet and the appointment letter is on letter head which is not yet signed by MD nor by me, only HR had signed it. Is it a serious matter if I quit the job and cheque get bounced or sign mismatch.?