After trying to find an answer to this for months I decided to make a post. After converting my contacts from my old Windows Mobile Phone to a Note 3 I have exactly one contact with an issue. The issue is only in the text thread and is a problem when I try to send a text to the contact from the preexisting thread. The contact number at the top of the screen (below the name) has a letter in front of the number for some reason. The letter is not present if I go into the contact or if I export the address book to a spreadsheet through Gmail or Microsoft Live. I tried deleting the contact from Gmail and Live to see if it will start a new thread or fix the error, but it does not. The issue is not present when I create a new text to send to the contact so long as I am not doing it from the preexisting thread, but then everything ends up in the preexisting thread instead of a new thread.
Hopefully someone here can walk me through a backdoor way of editing a text thread to fix this issue with the random letter in front of the contact's number so I can have regular text conversations with this contact without deleting the entire thread and message history.