Misusing signature

I applied for a Personal loan , the bank representative informed me my rate of interest for the loan will be between 10.49 to 12.49 and this will be calculated post verification and my CIBIL score etc, He has taken my signature and after few days I got my account credited with money @14% rate of interest. I complaint to the bank immediately without spending any money. But the bank forced this loan on me with higher rate of interest. Further I have savings acct with this bank and this account was opened 7 years ago. Recently I visited the bank and gave them a cheque to close my previous loan. The cheque got returned saying my signature did not match. When I checked the signature on the loan application form the same did not match with bank records either. The bank processed the loan without keeping me informed about rate of interest, though my signature is not matched with their records. Now when i tried to close my loan with the same signature they say the signature is not valid and charged me an additional 1500 as interest. What can I do in this matter. Please help