If you are purchasing oils and filters from 3S, you don't need to go to road side mechanics for oil change.
I take my Corolla and Mehran to 3S and tell them just to change the oil, no 10,000 or 15,000 KM service.
Just for oil change, Suzuki charges you around Rs. 200/- and Toyota charge 250/-
The OP must have availed 10,000 KM service, that is why they charged Rs. 1500/-