spam calls

can someone please tell me why i keep getting calls from the comcast number only to have it turn out to be spammers, cyber thieves or jerks trying to get my information. they use the comcast nuber so i think it is someone from comcast. i can tell it is a spam call because of all the background noise. you would think that for all the money we pay for the services provided by comcast we who still have landlines wouldnt be getting these types of call. if comcast cant protect themselves and we are only allowed 25 numbers to block then how are we supposed to deal with this