Welcome to the forums. You're talking to other customers here.
The design of the CallerID system pre-dates Internet based phone calls (VoIP). When a call is place from an Internet phone, it can insert any CallerID it wants. Mainstream consumer VoIP providers don't allow this, but commercial providers, do it your selfers, and some unscrupulous providers make it easy. You're most likely getting junk calls that are sending bad CallerID on purpose.
The act of putting a fake number into CallerID is called "spoofing," and there is nothing that can be done about it with the way the current phone system is designed.