A bug in iOS 13.3 allows users to easily circumvent the Communication Limits feature. While Communication Limits is supposed to block users (specifically children) from communicating with or adding unknown or unapproved numbers, simply setting up the phone to not sync to iCloud will bypass the feature and allow users to add new numbers without verification.
https://www.notebookcheck.net/New-bug-in-iOS-13-3-allows-kids-to-circumvent-Communication-Limits-parental-controls.447233.0.html