You know at my job a lot of our new recruits don't know how to handle customers, so theyre taken advantage of and talked down to. In my experience the best way to handle them is to stand your ground. You don't have to be mean, but you have to be unshakable in your resolve. You put your foot down, this is the way things are and I cannot and will not change it at your whim, if you have a problem you can take it up with management. Thats usually enough to dissuade most of my customers. Now rarely do I get rude customers, most of them like me and are happy with my efforts but once in awhile a Karen strolls along. As long as I do my job right, there is no fear of repercussion or backlash from management so I dont worry about it