Relieving Letter - Experience Letter

Hi,
Could anyone through some light on how to get the relieving letter and experience letter from the previous organisation. While I was seperating they said they would provide along with F&F. But now Non in the HR dept were responding to my mails.. when ever I speak to them they tell call next day...
Regards,
Siva Kumar

Did you complete all exit formalities?
If yes, send a written request by Regd post for relieving/exp. letter. Wait for their response within 2 weeks.
Pon

Pon,
I had send the register post 2 months back itself and preserved the acknowledgmen copy as well..
Tell me what do i do now.
Regards,
Siva kumar