Increase in repayment period of education loan.

I took education loan in 2013 for my engineering. Repayment period is of 10 years. Sanctioned amount was 3.5L. But we didn't paid single rupee. Because after education I started preparing for competitive exams and I started suffering from random health issues. Because of all that I never had any income. Last year in Dec we got a call from bank that account is going NPA and you have to pay amount of 90k and EMI is 30k. We paid total 2.1Lakh in a period of 4 months(all these years loan amount became 5L+ and now again it is near to sanction amount). After paying 2 lakh I asked manager to increase my repayment period so that we can pay EMI of 4-5 k per month. He agreed (I wrote a letter for that). But now after few months I started receiving calls that I have to pay 60k EMI and due of 1.2Lakh. I don't have job. I again ask manager to increase my repayment period (manager has changed now, last manager did nothing) by giving reason of my health, manager asked for medical certificate. But no doctor is giving me that( Because I had multiple health issues over the years). What reason should I tell manager for loan repayment extension???