I made my res. on-line then changed it to get a lower rate. When I get to the airport they try to charge me for the higher rate (once much higher). I always bring a copy of my confirmed res. so it's not a problem getting them to fix it but I'm getting annoyed. This has happened both times we've used Avis. Oh and I never have 2 standing res. by the time we go on our vacation so it shouldn't be that.