Swindling customers and very rude Manager

With the rising fuel costs everyone rushed to the garages to fill up on Tuesday evening at our closest Shell Garage on Rifle Range. On topping up our tank which was more than 3/4 full but we just wanted to maintain a full tank our petrol attended went from 1 right to 19litres.We asked to be shown evidence linking that our fuel was that much more considering we know our vehicle quite well and know that it did'nt need a top up of more than 11litres which at first the manager Ernest concurred with .On showing us previously slips we found that the slips they were showing us an hour before slip and ours of which the last person at the tank was literally a minute apart from. Ernest and attendant #3 handled this situation very badly and told us not to teach them how to do their jobs , they have no etiquette whatsoever in dealing with customers .Up to now no resolution has been made and i am warning all other motorists to stay away from that filling station if you dont want to ******** from your hard-earned cash. I am an avid Shell customer but this petrol station has left a bitter taste and some thing is definitely not right with their pumps