Byju's — Refund

I have bought bjus ias course for one year. They initially charged 14k for installation.
Within 15 days o have asked for the cancellation due to family situation. I have informed through mail [protected]@bjus.
But they not respond me late of one month.
After one month back they called me and said your refund validity was expired.
More than 17 times i have send mail.
They keep on telling the same thing again again.
What i have to do?