Injustice on Hoam loan with HDFC bank

Location/place: Pune

Name of company/service: HDFC Bank

Hi,
I want to raise issue with respect to HDFC bank interest rate changes. Whenever there is circular on interest rate increase bank immediately increases interest rate on existing as well as new customers, however when there is reduction on interest rate banks apply it only to new customers. This is extremely unfair & not acceptable.
In my case I was asked to pay INR 12,200/-in case I wish to get the benefit of interest rate reduction which happened some months back. HDFC Bank call this as ‘Conversion Enquiry’.
In first place why should bank ask me for additional amount for providing interest rate reduction benefit? Secondly why is the interest rate reduction applicable only to new customers when 90% customers have availed floating rate interest scheme?

Kindly support to get convincing answer.

Regards
Vaibhav Argade