I am a veterinary technician, and it is very annoying when I go into a room to talk with a client and they are on their cellphone- and expect me to wait while they finish their call.
I will pause for a moment to give them a chance to end the call ,but if they dont, I leave the room, and I return when I am done with whatever else I decide to do- be it another client visit, or labwork, etc. I have had people stick their head out of their room and tell me, "Im off the phone now"- okay, thats nice, I will be there when i can..
Also, the gas station across from my work- I have never seen the guy not be on his phone. He never stops talking even when he rings my order, takes my money, or gives me my change. I avoid that store unless it is really necessary because it is so rude.