Signed an appointment letter and then rejected the offer

Hi I have signed an appointment letter with company X. Along with this company I had another offer with company Y. The company X didn't give me an offer letter and gave me 5 mins time to sign the appointment letter. It didn't get the witness signed in front of me. When I asked they said they will get it signed by their employees afterwards. There was section in the appointment letter stating that i need to pay 3 months salary if i don't join by the committed date which is 75 days from the date of signing this letter. The one who referred me to this company X had given me a good feedback. When I asked the HR on employee lay offs and bonds that i need to sign after joining the company, they said no lay offs and no bonds are required. To my utter surprise I heard few interesting things about the company from ex-employee before 15 days of joining. He said there were 6 employees laid off in the past 2 years and the employee needs to sign a bond of 2 years initial for the training he was provided. With hearing this I reconsidered the decision of joining Company X and had mail them indicating my inability to join their company 14 days prior to the date committed. Then the real torture started, they kept on calling me and also intimated me through sms that if i don't join their company their legal department will sue me according the appointment letter. Also, i heard they started harassing the employee who referred me and put pressure on him to make me join. Given this type of company i decide not to join the company and intimated the same through email 9 days prior to the committed date. Their HR now has sent me an email asking me to pay 3 months salary as per the liquified damages caused by me for not joining with the pdf containing "BY RPAD" within a week time from this mail. I am not in position to pay that much amount and also not willing to join the company after this much of treatment. Can you please guide me on how to proceed from here? Thanks Ramesh