SCAMMERS

WiderMouthOpen  is correct.  You can't block an outgoing call.  You can only block your name and phone number from being displayed.  Using Caller ID Per Call Blocking (cox.com)

I don't think you can block individual outgoing calls. Just curious, but why would you want to? Does the scammer ask your mom to call back?

There are a couple of things you can do to block incoming calls.

First, use Voice Tools to block spam callers.  https://voicetools.cox.com/

Voice Tools > Settings > Spam Blocker: Customize

The phone won't ring for blocked numbers, but they will appear in Call History.

Second, use phone codes to block up to 25 selected numbers.  

• When you hear a dial tone, enter *60
• Press 2 to add phone numbers to be blocked.
• Enter the number to be blocked and press # or just press # to block the last number.