Ever since updating to the latest ios18 I have had virtually no cellular connection. Even with four full bars I can’t actually connect to service. Sometimes I’ll get notifications, but sending anything, Waze, websites…not a chance. I sure hope they fix this fast. What’s the point of a smart phone and iOS that makes a phone unusable??
You're on a beta version of iOS; there are going to be issues.
You should probably raise this as a bug in the usual way. It won't really get progressed if it's only posted in these Developer Forums.
You need to raise each issue you find separately at https://feedbackassistant.apple.com/ You can post the FB numbers here if you want, so that others can link to them.