My company not giving me relieving order ?i tried a lot, they are

Respected Sir/Mam, I Worked in private it company in nungambakkam Chennai , I joined here in June 2014 for the past 1 year I worked here, recently I got an offer in one American MNC and I planned to resign my job, so I spoke with my manager regarding this on 16th June 2015, she got anger and she said "ok you put a mail to HR , he will take care of it" so I put the mail, she didn't reply for it. Then after 1 day 17th June 2015 evening HR called me and said that " I give you 1 hour time you have to leave the company write your resignation letter and give me ,give your id card and leave the company" I wrote resignation letter and I signed it too and gave to him, I requested lot to give a copy of resignation letter, but they send me out. without resignation copy or relieving letter I can't join in new company. I requested them with many people's they saying that it's our policy if anybody leaves the office before 2 years we won't be giving them relieving letter, I requested them that ok but please give me resignation copy , they saying if I give you will join in new company and you should not join that's our aim. Kindly help me something in this issue, or give me any suggestions to move further., also I don't know what to do. HR threatening me that if you do anything to get relieving letter or copy of resignation letter we will spoil your career, we will say bad about you if any background verification came to us. I didn't sign any service agreement, like I accepting that you no need to give even a copy of my resignation letter. Also there is no such rules in offer letter, they said orally that we won't give you experience certificate, but they didn't said we won't give you even a copy of resignation letter. If I get a Xerox copy of my resignation copy and if they didn't say anything wrong about me that's enough for me, kindly do the needful as soon as possible. Because Joining date in new company is nearing I want the copy before this Thursday kindly do the needful. I don't know whether they doing this is correct or not as per law, kindly give me any suggestion, if that is wrong please do some action and get a copy them, this is my career my life, every day I am getting afraid of this. Kindly do the needful. Awaiting your response. Documents I have, Appointment letter of current company Pay Slips Appraisal letter Id card copy Bank Statements.