Blonde cell phone

A young man wanted to get his beautiful blonde wife something nice for their first wedding anniversary. So he decides to buy her a cell phone. She is all excited, she loves her phone. He shows her and explains to her all the features on the phone.

The next day the blonde goes shopping. Her phone rings and it's her husband, "Hi hun," he says "how do you like your new phone?"

She replies "I just love, it's so small and your voice is clear as a bell but there's one thing I don't understand though."

"What's that, baby?" asks the husband.

"How did you know I was at Wal- Mart?"