I changed the thank you letter address, saved and then re-published HOWEVER it still keeps sending out the wrong letter.

I have gone back in to verify and if I copy the URL inserted and type it into a search it goes to the CORRECT letter but for some reason it keeps sending out the original incorrect letter.  Do I need to change in a different place as well.

I am not quite sure if you mean thank you page or the autoreply (sometimes referred to as thank you) email?

If you have the issue with the thank you page, then you would need to change the thank you page within the Thank you page wizard. You would also need to change any setup within conditions related to the thank you page as well.

if you are however referring to the email that is sent when the form is submitted and some link within the same, please do note that you should check the body of all emails and then change them accordingly.

We would be happy to assist if you can give us a bit more details in regards to what exactly happens.