Most colleges today will consider phone use during a test cheating, then it depends on the school but at least a 0 on the test is likely. I've had some professors say upfront that they'll go further and wreck cheaters as much as they possibly can.

They probably don't ask for phones upfront, but I don't see how that'd do anything. The only way to make this stricter would be to search students like they do for big standardized tests.