sorry for creating confusing, let me put all the things in perspective. I bought Wagon R in july 14, soon after buying i notice this humming sound it is more prominent because i park my car in office building basement so any sound is amplified in closed area, One noise is when you insert key and turn it one step, you will hear engine check noise this includes multiple parts checking noise combined, once engine check is complete check light fade out and sound usually gone too, but when you start that car and notice is quite place you will hear continuous humming sound this noise is more when petrol tank is full.
So to check this i went to 3s, checked the car parked in showroom, i asked the dealer to make ignition and let me observe the sound, i went to the back of the car near fuel tank to hear the noise clearly and i could easily hear the sound, fuel pump is in fuel tank and it is noisy but it has no fault. Even i talked to suzuki people who visited the showroom to inspect the cars for warranty claim and the guy said it is loud but is has no issues. If you google it, you will find that fuel pump tends to be noisy but not all of them.