Wake-up Call is a novella written by Diana G. Gallagher. It was first published in 2001 and was the thirty-sixth book in the Sabrina the Teenage Witch book series.
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Cell phone cat-astrophe
When Salem tells Sabrina her aunts are going to get her a cell phone, she's thrilled. She'll be cool at school, and will be able to check in with her friends 24/7. So when Sabrina finds out that Salem was teasing her, she's totally annoyed, until she comes up with her own plan to have a phone -- magically.
Problem is, magic phones can be a touch tricky. Sabrina's new cell keeps ringing, and won't shut off. Will Sabrina get the message before she gets into big trouble?