Friends Not Having a Phone

I hate it when my friends don’t have a phone of their own! I called my friend to give her a heads up on a party that was moved an hour later, and her mom answers, saying she was busy. And I was so embarrassed! Like, maybe I disturbed her, I should’ve texted, etc. Oh my, instead she should’ve given me her e-mail, or Facebook page. There’s also the problem that I can’t just text/call her whenever I just want to communicate with her.