Well the best thing is to get in to habit of having a several filling stations that you know by experience or through other's recommendations to get your vehicle filled regularly. Further, if you can try to find a near by station that is owned and controlled by armed forces. They carry out daily pump checks to see whether the pumps are pumping exactly the amount indicated. This is done by different people very day and documented. So there's very slim chance of being cheated.
Further, if u are planning on getting a full tank, just have a mega bottle with you where u have a marking on to indicate how much a 1 liter or 1.5 liter would be. Then ask the station to pump a liter to it first. Just say its for backupJ. If the amount is right get what ever amount u need. Otherwise complain.
I don’t know whether they can switch the calibration of the pump instantly, but if they can the bottle method wouldn’t work. Further,, I read a member has mentioned all stations much have those one liter and 5 liter containers with them to measure right, well most of the places have them, but not all, and some have rigged containers as well too…