I seem to be limited to a small number of phone numbers I can block. Anonymous Call Rejection doesn’t work for callers that simply use fictitious local phone numbers and add the city and state. I would think a company as big as Comcast, with the technology available, that I pay so much money to for service, could provide better call blocking capabilities. Telemarketers simply rotate numbers when they have one blocked. Call blocking should be unlimited and extremely easy to use.
Call Screening allows you to create a list of up to 25 callers who will receive an announcement saying that you aren't available. Please note that this feature is separate from Anonymous Call Rejection, which blocks calls from callers who have their Caller ID information suppressed.
As far as the fictitious numbers and inbound calls you're referring to that can sometimes get by, have you heard of Nomobo? You can find more information about it here: https://www.xfinity.com/support/articles/nomorobo.
You can also add your number to the National Do Not Call List. Add your phone number to the National Do Not Call Registry for free by visiting: https://donotcall.gov/ or by calling 1-888-382-1222 (TTY 1-866-290-4236) toll-free from the phone you wish to register.
A combination of those few things should help reduce the amount of unwanted calls you're receiving. If you have additional questions, please let me know.