Legal actions

Hi,i joined a start up market reserach company on jan 2016 and quit on march 2016 due to lot of micromanagement and pressure.I had health issues and i hve breathing problem and bronchitis.I have the certificates as well.I did inform my sales head about it and wanted few weeks of medical leave.Few days after i gotta call from the director and he charged me of abrubtly leaving the company and to meet him.I did inform him that once i get little better. i will come and meet him and complete tthe formalities cause i cant continue to work and i need bed rest.Now being informed by me via calls and messages they say i have abrubtly left the company and they want me to pay them my 2 months salary and also threatened me to send legal notice stating the same.I have been very polite and good to them but still they are using legal tactics.I do want you to know that in my offer letter they have an obligation stating if i quit before 8 months i am liable to pay them salary for 2 months.I am really confused and disturbed.Plz lend your ecpertise