Mr. Joshi has given valuable advice. Kindly follow it.
It seems that the company has tricked you. Companies do take advantage of ill informed employees.
Employee should consult elders in the family, experienced and competent well wishers, trained legal mind, lawyer/law firm before acting in haste and signing any document.
You have posted that:
--"i aggred the same & worked till 05.06.2012 in company." Did you receive salary for May,2012?
--If you have sent just a SMS and stopped going to Office Company may declare you absconding.
--"Now, i got one letter from company stating that i have not serve my notice period.'" This letter implies company has acknowledged your notice/resignation. You would know what is written by you in apology letter. Did you withdraw your previous notice/resignation, and submit afresh notice/resignation vide your apology letter?
You have the option of requesting your appointing authority to let you examine your personnel file.
You must reply to company's letter and offer to either serve the balance notice period or adjust notice pay in FNF statement. If the notice pay is adjusted in FNF statement and notice period is bought by next employer, you shall not be adjusted to double taxation Company shall claim notice pay from the date of resignation which can be first or second notice( apology letter) given by you.
You may claim that the apology letter was collected from you under coercion/pressure in office.
You may reconcile and agree to serve the balance notice period counted from the date of 13.03.2012. If you are able to do so you should obtain the original apology letter or a copy and withdraw it.
You should obtain a written consent fro your next employer that you shall be absorbed without any relieving letter and on the strength of copy of your resignation alone.
Show all of your documents, records, to your lawyer and let your lawyer draft your reply/representation or issue a legal notice.