Hello Grug7,
Welcome to the Apple Support Communities.
Please be sure to follow these instructions when setting communication limits for an iOS device: Set up Screen Time for yourself on iPhone
If you are noticing that the limits change unexpectedly, you may consider Enabling Screen Time Content & Privacy Restrictions so that a passcode is required to make changes to communication limits: Use parental controls on your child's iPhone, iPad, and iPod touch
If the instructions above do not help to resolve the issue, please disable Screen Time, restart the device, then try to set up Screen Time and commutation limits again.
For more help, please contact Apple Support.
Have a great day!