The brutal truth of the matter is that Tracfone, or any other PAYG provider, has absolutely NO INTEREST whatsoever in implementing a call blocking feature for their customers. Why would they, since those types of calls result in BILLIONS of minutes being billed to their customers each year?
And the most often quoted 'solution', which is to set calls to silent ring, is actually no solution at all, since unanswered calls get passed to voice mail, which the customer also pays for.
The most cost effective solution is answer/hangup, which is available in many user installable apps for those that have Android or iOS phones.
There is a way to implement answer/hangup on the LG840G (or similar) phone.
When I get a 'repeat' offender, I save the number in my Contacts, named Do Not Ans 1, 2, 3, etc.
I also use the following picture to identify the Contact-
When a call comes in, and this picture comes up, I know to answer and then immediately hang up the call.
It's by no means a perfect solution, but it is the solution that costs me the least!
"The differences between how you act when people are watching, and how you act when no one is watching, define who you really are."