Comcast lets you block up to 12 phone numbers who will eventually get the message that you “are not presently accepting calls.” You will need to know the number before hand. Here’s how you can do it :

Steps for blocking a phone number on Comcast

  1. Lift your speaker and press *60 once you hear your dial tone
Source: WikiHow
  1. Follow the instructions of the voice prompt and put the first phone number you want to be blocked with the area code and the seven-digit number even if its a local number
  2. Listen to the confirmation of the number being added and move on to the next phone number you want to be blocked
Source: WikiHow

How to forward calls with a Comcast phone

Our hectic lives require us to attend hundreds of calls every day. However, you might receive unwanted calls in the meantime which you would want to avoid in future. To do so, you can forward the unwanted calls to other numbers including your cell. 

Steps for forwarding calls with a confirmation call

  1. Pull your receiver and dial #72 once you hear your dial tone. Wait for the dial tone to return.
Source: WikiHow
  1. Put the number where you want to forward the calls. Tap 1 and put the area code as well
Source: WikiHow
  1. Wait for the confirmation cell on the number you wish to reserve for forwarding calls. If you don’t receive any call repeat this process after about two minutes to activate the forwarding
  2. Wait for a confirmation tone. The forward is activated only after you get the dial tone from the other side 
Source: WikiHow

Steps for forwarding calls without a confirmation call

  1. Wait until you hear the dial tone
  2. Dial *72 followed by the number you want to forward calls to. Press 1 and mention the area code        
  3. Listen for a confirmation tone. Forward is activated only after you hear the tone 
Source: WikiHow