I just came across this great poster in The Innovative Educator Blog which can help you educate your students about cell phone etiquette. It contains some great tips on how students should be using their phones. Try to print it out and post it on your classroom wall for everyone to read.
If you want more educational posters to use in your classroom then check it out this link http://www.educatorstechnology.com/search/label/educational%20posters
Via Gust MEES