I tried to sign up to Twitter earlier on this week, I was using my home internet but skipped the phone verification when signing up. I had not even posted a single message when I received the message that their was suspicious activity on my account and I would have to provide phone verification to continue. It annoys me that these companies require you give them your phone number and don't offer any other way of proving your account is genuine. I am sure its nothing to do with verification and all about harvesting even more data they can use to target ads.
Long story short is that I am not going to sign up to Twitter after all, unless I buy a burner PAG SIM card for signing up for such services so I can keep my real number private.