Twitter 2 factor authentication

Since July 6 Twitter has been asking me for a two factor authentication when I try to login. I don't have one or a backup code. I have contacted twitter support but they just reply with a standard answer advising to login to change my settings. If I could login There would be no problem. It says use the app to get an code but I can't login on any device. They have my phone number and I've asked for backup code by SMS but nothing. In the absence of support from twitter, what can I do?