Most people have cell phones with cameras today. If you think somthing is up GET A PICTURE of it for proof when you make a complaint. I have seen odd pump behavior over the years. Just this week a guy noticed the price per gallon on the pump was .04 more than the sign said. He complained to the clerk and just got a "whatever". He took a picture called the local TV news and they came out (still over charging!). They are now looking at MAJOR fines from the state. They do not know how long it was like this so it helps to pay attention.
Another time was was pumping gas and it clicked off while I was cleaning my windows. I went over to the pump and the numbers were still clicking by! I complained to the clerk and got the sholder shrug. I filed a complaint but never got a response. I never went to that station again.