I too have a loan with Citibank. I wrote to them, simple letter, asked them to revise the interest rate because I'm good pay master and have few home loan with them (actually co-name with parent) and also credit card with them for long time.

They called me and offer me peanuts, BLR-1%. not satisfy, told them in the market other bank offer BLR - 2 %. Then they counter offer BLR-1.3%, lock-in 3% for 5 years or 5% for 3 years.

All this only possible if you have pass your previous lock-in period, mine was 3 years.