Hi pearced0
welcome to the Apple (user-to=user) Community.
Re: Calendar: When talking on the phone : it won’t let me use the back tab it stays frozen"
If you haven't already, you could try updating to the newest available iOS:
About iOS 16 Updates - Apple Support says iOS 16.5.1
Else: Wondering if you have tried restarting your iPhone : Restart your iPhone - Apple Support
(eg: deletes temporary files and often restores order if something is not working right)
And: What to do:
If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open - Apple Support
If you still continue to have that difficulty:
Seems the best people to contact would be iPhone Support.
There is a "Get Support" link at the bottom of their webpage (link below)
(You may be able to choose from online-chat, phone, eMail etc)
iPhone - Official Apple Support
You may want to send feedback to Apple:
They will likely not reply, but your info. will reach those who can make changes.
If others are also sending feedback on this issue we may see it addressed in future updates.
Web-form for feedback:
Feedback - Calendar - Apple
All the best :-)