How do I receive phone calls on iPhone that are not in my contacts?

Did you check the settings from the support article viewed at the top of this page?

Check your iPhone settings

1. Turn Airplane Mode on and off. Go to Settings and turn on Airplane Mode, wait five seconds, then turn it off.
2. Check Do Not Disturb. Go to Settings > Focus > Do Not Disturb and make sure it's off. Learn how to use Focus on your iPhone or iPad.
3. Check for any blocked phone numbers. Go to Settings > Phone > Blocked Contacts.
4. Check Call Forwarding. Go to Settings > Phone > Call Forwarding and make sure it's off.
5. Check Silence Unknown Callers. Go to Settings > Phone > Silence Unknown Callers. If the setting is on, a caller must be listed in your Contacts or Recents. Or they must have shared their number in Mail or sent you a message using that number in order for their call to go through. Add their number to Contacts to ensure the phone rings. Calls from some third-party apps might not go through.

The most likely reason is step 5, where the phone is set to silence all unknown callers.

You asked this question twice.

How to receive phone calls that are not i… - Apple Community

Please do not duplicate your posts.

You likely have Silence Unknown Callers turned on. Go to Settings > Phone and Turn off Silence Unknown Callers.