Foolednomore, I'm very surprised that you are receiving so many letters from JWs.
The idea of sending it "Return to Sender" good but it would be wrong to write "Wrong Address" on it if it was actually addressed to the right address and to the actual person who lives at that address.It might violate US postal use laws to write "Wrong Address" if the address and addressee are not wrong.
I think one can write "Refused" on it, and thus "Refused - Return to Sender" on it. Keep in mind that the post office will only return letters to the sender if the mail was sent First Class (or Priority Mail?), instead of by a discounted shipping rate. But, letters sent by the JWs (in the USA) for witnessing purposes are probably all first class mail.
The idea of writing things on the back of the envelop as suggested by truth_be_known also sounds good to me, except I think one should be careful of what ones writes. Otherwise, the JW elders might get the idea that the addressee of the letter is now an apostate, instead of merely an inactive disinterested person.
Foolednomore, here are some reasons why I think you might be getting the letters (though the ideas don't explain why you are getting so many) despite requesting to be on the don't call list, and what might be a better approach to stop receiving the letters.
- Perhaps the letters are being sent by people in a congregation which you never attended, though likely from the same Kingdom Hall. If so, those people probably wouldn't know you are on the "Do Not Call" list (unless your home is in the territory of the congregation of those who sent you the letters).
- I think the "Do Not Call" list is usually kept with the territory card that is used for door to door witnessing. If that is the case the people writing the letters, even if from the congregation you attended, likely wouldn't know you are on the "Do Not Call" list.
- It might be advantageous to browse through the contents of the letters to see if an email address is provided by some of the senders. If so, then if you email the person to stop contacting you, and to notify the keeper of the "do not call" list of such, while stating you will never return to being an active JW, maybe that will stop the letters. However if you email the people, then that might result in receiving emails from them.
- In the past few years I have only received two letters from JWs (other than from my mom and sister). The second letter had a personal email address and I sent an email to that person. The person then sent me an email saying she would inform someone at the Kingdom Hall to make sure I stop getting such letters. I did not receive a further email from the JW (nor from any others) and thus far I have not received further postal mail letters from JWs (other than from my mom and sister, of course).