A phoner is a someone who has entered a store of some type while on their cellular device and who then attempts to perform some form of business transaction with a clerk. They use rudimentary forms of gestures and facial expressions to try and inform the clerk of the item they would like to purchase. They rarely use words and if they do it is in low tones, so that they are not rude to the person on the other end of their conversation, but also so they will be nearly inaudible to the clerk.
Clerk: One day I am going to shove a cell phone down a phoner's throat.
Clerk: I just had to help ANOTHER phoner. Why can't they just ask the person they are on the phone with to "Hold on a moment."?
Clerk: I hate phoners; they are so rude!
Clerk: I just hung up that phoner's phone while they were in mid sentence! (This is usually fallowed by a high-five from another clerk.)