Full n Final settlement

I joined a big MNC in Jan 2013. I continued till Dec 2013 when a FIR got lodged against me u/s 304B due to my wife commiting suicide. As a result, I need to go to jail and didn't got a chance to resign. I got a bail after an year but in the meantime, my organization terminated me due to absence from my duties. Although I informed them about the incident and my inability to come to office via email and later also had telephone discussion with my manager and HR. Now after I came back, I completed my exit formalities and got an experience letter too. Now they have sent me a full n final settlement bill where they are asking me to pay one month salary as I didn't served notice period. There was one month notice period in my organization. What should I do now? Whether to pay them, or It can be waived off as I was in a situation where by no means it was possible for me to continue. Also I never resigned, they have terminated me and I am also ready to join now. They don't want me to join, so is it OK if I don't pay, what can be the consequences? Will it have any effect on my future endeavors? Or an experience letter is enough for me to move on?