Cell phones and a pleasant demeanor

I saw you walking towards me the other day, and I was ready to greet you with a big smile and a warm hello. Then, I noticed that you were talking on your cell phone. And so, instead of a cheerful greeting, we settled for awkward waves.
During the summer months, we study Ethics of the Fathers every week. One of the enjoinders in Ethics of the Fathers is "Hevei mekabel et kol ha-adam be-sever panim yafot: greet each person with a pleasant demeanor."
Avot d’Rabbi N. (33:4) teaches: “If a person gives his friend all the gifts in the world with a sour face, he has given him nothing. But one who receives his friend with a cheerful face, even if he has given him nothing else, has given him the greatest gift in the world.”
That same evening, I listened to Rabbi Wallerstein on torahanytime.com speaking about the use of cell phones. He described how people approached bank tellers and cashiers, gesturing to them, while talking on their cell phones and treating them with a total lack of respect.
The following day, I went to the supermarket. The cashier opened a new register and I was the first on line. Seeing that there was no one behind me, I started talking to her. I introduced myself and learned that her name was Tanya. She had been an owner of a Chinese restaurant for 20 years before beginning her stint as a cashier.
The next time Tanya sees me, I hope she will recall me with warmth, as the person who initiated a conversation with her, and not the one who treated her with total disregard as she was too busy talking on her cell phone.