Notice recovery amount

Hi All, I was working in an IT company for two month only, Due the health issue I had to leave the company and go back to my hometown. Before joining to this company I was serving with some medical conditions so could not continue with the last organisation. In this company I resigned from non official account they denied and asked my to give the official resign which I supposed to do but they already marked me as abscond. Now after two month they are asking me to pay 42k amount as a notice recovery. It is not mentioned in my Offer letter about this. Please suggest me what should I do in this case? I'm not earning right now not even working in any other organisation. if they want now I can serve my notice period, I was in a probation period for three month to the company and according to the letter 15 days will be the notice period. Please suggest me the solution I'm very depressed and mentally harassed by the company . Thanks