Twitter forces all new users to enter a valid phone number
They have been doing this for any account registered from a VPN or Tor. However, you can simply appeal the block and tell them you haven't tweeted and not broken any rules.They will send you an automated mail, offering to validate your phone number, or reply to the mail if your problem is not solved. Just reply to the mail.Unfortunately, processing the request takes anywhere between 10 minutes and 2 weeks; usually a couple days at least. I assume this is on purpose to make it cumbersome for spammers.They always reply with the same boilerplate, but the account will be unlocked:  Your account is now unlocked, and we’re sorry for the inconvenience.
   
  Twitter has automated systems that find and remove automated spam accounts and it looks like your account got caught up in one of these spam groups by mistake. This sometimes happens when an account exhibits automated behavior in violation of the Twitter Rules (https://twitter.com/rules).

  Again, we apologize for the inconvenience. Please do not respond to this email as replies will not be monitored.