I've had Cox phone for years and have excellent service. While not Cox's problem we get a lot of robocalls. I've asked Cox to implement something like Nomorobo. However I understand the FCC will currently not allow the phone company to block calls. I can see why this law was originally created.
I've looked into the Cox phone blocking tools and find it not helpful in our situation. Due to the ability for companies to spoof caller ID numbers, the phone numbers used and random and not predictable. Some calls show our home number on the caller id display!
My solution was to purchase a truCall device from a company in the UK. We purchased it about 2 years ago and have no robocalls since (well maybe a couple). The box is given a list of phone numbers you want to let through (friends etc). These numbers go through to the phone. For call numbers not on the list a voice comes on saying "we are screening calls and please press number 3 to go though" (or something like that). I believe the number changes periodically but not sure. The result is no robocalls enter the number so are hung up on (without ringing the phone). Yet calls from say your doctor can still go through without an issue. There are many other options but this is how I've set ours up.
Its a little costly and needs to be located when it can intercept all the phones you want to screen but we found it to be very much worth the cost.
I'm a little hesitant to post this message as if this product became very very popular the robocall robots would be programmed to circumvent such a device and I wouldn't like that. However if someone really want to block the annoying robocalls it is great.
JohnRob