Steal
Twitter and I had a funny game. After TRAs got me banned for a bit, Twitter demanded I enter a phone no each time I logged on.
Previously I'd given Twitter my number permanently and got lots of silent calls in my 1st week. I phoned every number back too as I was curious and happy to speak to their parents, but they didn't answer or the number was out of service. Little weasels.
This time, I didn't want to give my number, but each time I logged on I'd give it. As soon as I was logged in I deleted my number, but each time it demanded it again.
In the end I closed my account. I now have a new one, but I just look and don't post.
I'd definitely get a cheap phone or £5 SIM. The TRAs must have racked up loads of them by now!