Bajaj Finserv — personal loan - roi cheated

Address:

Hyderabad, Andhra Pradesh, 502032

I took rs 96, 000/- loan from bajaj finserv (Lan 400pst[protected], they committed 21% roi for the tenure of 4years but after getting a loan when i saw repayment plan they are charging me 34% by saying 21% flat roi.
Emi amount got changed drastically from 2, 975/- (Which is supposed to be) to 3, 684/- basically they are charging interest rs. 80, 833/- instead of rs.46, 814/-

Which is double the interest and almost equal to the loan amount. They playing it underhandedly.

Please help me out with the situation.