Cell phones at test centers?

It's true--you can't bring cell phones (or any similar mobile devices) into the testing center. However, there are provisions for this--many test centers provide lockers outside of the exam room for personal belongings. I'd call your testing site to see which provisions they provide (ie, lockers, directing you to a nearby pay phone, etc). This is definitely a common concern, so your test center should have a way around this.