Fares overcharged

I would just like to bring it to you attention. On numerous occasions your drivers stop at the petrol station to put in petrol. This happen to me the driver accepted my ride and on his way to me he decided to stop at the petrol station before making his way to me. Uber charged me extra for this. They tell me for the time and distance this is the correct amount charged. No its not. The reason for the extra time is because your driver made a unnecessary stop at the garage. Why did he not put in petrol before accepting my ride. I just find this unacceptable. I would not advise anyone to use uber for this reason.