About interest charged by citifinancial on personal loan?

I want an legal opinion whether the Citifinancial has the option to charge interest rates on personal loan varying from one person to another in the same city? is there some way I can ascertain the actual RBI directive on this? I have been paying my installments regularly but the finance company has not kept its side of the assurances to reduce the interest rate till now, though it was supposed to have been done 9 months ago. Can I seek the court's help or whom should I approach for solving the issue? the interest rates are exorbitant! is there no law to protect my interests. I have sincere intentions of repaying the loan EMIs but with reasonable interest rates. Kindly advise