Byju's — Want refund and cancel the course

I bought the course in February from byju.. I took trial classes but i faced problems in taking online classes.. I unable to understand topic. And the financial conditions of my family are not good. That's why I want to cancel the course and want my refund back.
I tried to contact counselor and customer care through call but I did not get any response from them.They are not refunding money and also collect another emi from bank..even though i am not taking any classes.