State Bank Of India [SBI] — dom surcharge/tips deduction

RS44.20 got deducted from my SBI account as DOM surgharge/tips,
I had no idea why it got deducted until I searched online, why should the petrol station charge us for using debit card to pay? and y don't they inform us regarding this in advance?I made a transaction of 1500 and according to the SBI site they should have charged 0.75% for transaction upto 2000 on SBI PoS terminal and 2.5% for other Pos terminals.which eud come upto 11.2 in first case and 37.5 in the 2nd case, then y was I charged 44.2 for Rs1500???