Hi jhowton,
Thanks for posting in Apple Support Communities! Although the callers may not be in your contacts, their number may be picking up from recent calls or Siri Suggestions.
Incoming calls will come through from people that are saved in your contacts list, recent calls list, and from Siri Suggestions to let you know who’s calling based on phone numbers included in your emails or text messages.
Find more information about this in the following articles:
Detect and block spam phone calls
Siri Suggestions on iPhone
If the callers are not in your recent calls or someone that may be in your Siri Suggestions, we suggest restarting your device as it can fix many issues. Should the behavior continue, contact Apple Support for further assistance.
Cheers!