How do you know?

For their first anniversary, a man bought his young wife a cell phone. She was thrilled and listened eagerly as he explained all its features. The next day she was out shopping when the phone rang.
Hey, darling, he husband said. How do you like your new phone?
Oh, I just love it! she gushed. It's so cute and small and your voice sounds so clear. But there's just one thing I donít understand.
What's that?
How did you know I was at the sari shop?