Higher ROI on home loan as per RBI guidelines

I have availed home loan from PNB HFL on floating rate of interest in 2013. My ROI was revised 2-3 times till now and currently my ROI is 11%. In July RBI has announced to slash off ROI for all housing loans and PNB HFL started offering ROI of 10.25 % for all new customers. But when I enquired that why my ROI is not yet slashed off from 11% to 10.25%, they are asking to sign a stamp paper and pay some principle difference with 0.5% rate. However, since this is Floating ROI loan and its slabs revised as per market without any paperwork in past then why paper work is required now and what is the point paying difference.

I communicated these points with bank on email and they said, that for existing customer in market, home loan interest rates are still high. Lower interest rates are for new customers only. If you want lower interest rate than it will be based on your request and hence you need to pay the differential amount of some Rs. 4500 and give an signed notarised agreement on 100 rs stamp paper. Only then your request can be considered.