Scammers can fake their caller ID info, and using the number they're calling seems to be a popular trick. For more information see any of the many article links at https://www.google.com/search?q=caller+id+my+own+number, for example https://www.consumer.ftc.gov/blog/getting-calls-your-own-number.
Comcast won't let you block your own number, so there's nothing you can do about this without resorting to 3rd party hardware.
Possibly consider to port the comcast number an iphone with free unlimited-voice-and-text service, and set the iphone to send unknown-calls to voice mail without ringing the phone. Then turn off voice mail audible notifications too.
ps - Spam/scam phone-calls are not typically due to "hackers".