There is a federal Do Not Call list which is a big joke. You are supposed to list your phone number(s) with it and are not to receive calls from telemarketers or robocalls. There is supposed to be a fine of $1K for each call made to a number in the DNC list. I'm tempted to log such calls and turn them in to the FCC. Call waiting is the best thing to identify who is calling. I feel if it is important, they can leave a message and I'll call back if I feel it's warranted.
I have received such calls on my land line and cell phone.
I have never gotten any satisfaction from the DNC complaint department. Sorry, but they could stop this if they really wanted to do so. They don't!
I use a program called NOMOREROBO. It is freeware that redirects any computer generated call to your phone, to a dead end mail box. Your phone only rings once and that is it. Between it and caller ID I am usually able to effectively screen the telemarketers and spam calls.
You'll never stop them...only the governments can do that, but it seems that they are unwilling to do it.
Forget getting your cell providers to help. Mine, only wants to sell you a blocking service. It is big business for them as they end up making money from the cell traffic.
I just add the numbers to a "Blocked Call" entry in my address book. I used to have a "Silent" ring tone assigned to it, but Apple in their greed took the ringtone away several updates ago. I sure that you could purchase it from them at their store.
Annoyed by the spam callers, frustrated, buy the silent ringtone from our store and make us money. (Sorry, for the rant!)