Employment Related - Need Relieving Letter From Employer

I worked for a company for 5 months from apr to sep 2017. Decided to quit due to health reasons, but couldn't inform the company. i didn't respond for 4 days. Then I called and said my boss that am resigning and he asked me to send a mail and did that. HR called me and asked to surrender the laptop next day and I did that. After 3 months on dec 1st I received the settlement also. A week ago I mailed Regional HR for chances to rejoin the org. He responded politely that no vacancies and he will get back to me in future. Now i called HR for relieving letter, and she says that Regional HR is not signing. I called Reg HR and he is saying that u didnt inform properly and after a week of resigning u have gone to coffee day and put status. My question is I have received settlement from the company after 3 montha which means i have resigned properly. Reg HR has replied to the mail that he will get back to me if there is vacancy and he didnt mention anything in the mail. how do i proceed.