I received calls from 800 266-2278, which web search results say is used by Comcast.
-- The Caller ID is 1-800-266-2278, not "Comcast" or any other name.
-- When the call is answered by the answering machine, no message is left.
The first is merely annoying. The latter is grossly discourteous.
If this number is used by Comcast, please properly identify the call or, at least, leave a message giving a reason to answer when that number calls again.