My iPhone with iOS 16.3.1

Go to Settings ➜ Display & Brightness ➜ Auto Lock and set it to something else from there. You have options from 30 seconds to 5 minutes and "Never".

If you have no option for Never, then you may have a corporate Exchange email account or profile applying restrictions and disabling lock out options for your device. Check with your company's IT department in that case.

You can change the Auto-Lock time in:

Settings > Screen & Brightness > Auto-Lock.

You can also ask Siri to open the Auto-Lock menu, just say "Hey Siri, Open Auto Lock" if you want it to go a little faster. You can also create a Shortcut that you can place in the Widget Menu or on your Home Screen.

How to make a Shortcut for Auto Lock:

1. Open the Shortcut app

2. Press "+" in the upper right corner.

3. Press "Add Action"

4. Search for "URL"

5. In the URL field, paste this: prefs:root=DISPLAY&path=AUTOLOCK

6. Tap in the bottom line "Search for apps and actions"

7. Search for "Open URLs", and tap.

8. Give your shortcut a name, icon and color.

9. Tap the small "x" in the top right corner. Done.

Now you can add that widget on your home screen if you want.

If you have an email account added from the place your work at, it could restrict the options there. The Office365 installation may also have required a profile that adds that restriction.

As I said, contact your IT department in that case.