Fill out a feedback form for the request and provided 1. Copy of passport 2. Digital Delta membership card 3. Screenshot of recent Delta activities. I did have to do it few times and the customer rep keep asking a statement, which does not exist with Delta. I ended up contact local office and provided them the exactly same document, and was approved for challenge that granted me 4 months of Elite status, and with one international flight, it will be extended to 1 year.