Get a Call Blocker it's a $100 on Amazon or other blocker out there and you won't have this problem.
The blocker will block all "spoofed numbers", unknown, out of area, that are blocked automatically, and up to 80 numbers. All the numbers that Comcast won't block.
I get a least 3 to 8 calls a day the the blocker blocks and I don't know it till I look at the blocker screen.
Check it out for peace of mind.