Resignation

I have been working in nationalised bank since 10 months. I had left the job without providing any notice. I mailed them that I had been suffering from bad health and could not join the service. After 6 months I mailed them my resignation and I am willing to pay them 3 months salary which was written in my offer letter. But theg have constituted a medical board and asking me to report there and then they are asking me to regularise the unauthorised absence and only after that I can resign by the procedure laid in my offer letter. Is it neccessary to report to the medical board. The place where I work is about 1000 km away from my home. I have cracked another exam and willing to join there. What can I do now? I was absent for 6 months from my office and I do not want to join it again. Please guide.