A young man wanted to get his wife something nice for their first wedding anniversary. So he decides to buy her a cell phone. He explains to her all the features on the phone. She is all excited; she loves her phone.
The next day his wife goes shopping. Her phone rings and it’s her husband, “Hi hon,” he says, “how do you like your new phone?”

“I just love it, it’s so small and your voice is clear as a bell but there’s one thing I don’t understand. How did you know I was at the supermarket?”