I understand how you feel about cell phones but if they are on a landline phone how do you know they are not talking to the supervisor or to the store's phone (like customers calling in for help and advice on products in the store?)
My hearing daughter was with me, she can hear the Shop Owner's lovey-dovey talk on the phone.
Better still, the owner should asked the caller to excuse as there is customer waiting to be served, and telling me "Can I help you?" or "Won't be second" ? etc.