When speaking you just say the username.
You can't call Twitter.
you call a husband on twitter a twubby !
they have names like Xx_Puffypuff_xX because some people call it "cool".
It's also called Twitter.
An answerer, in this case, you can call him by his username, Ironnica
USERNAME
Yes.
Call Customer Care Service.
You would probably run into copyright issues as Twitter was originally called that by the creators.
Twitter doesn't provide any direct calling service on it's website. Call via any other VoIP service like Skype, etc.
Call your cellphone provider's blackberry department
call the isp (internet service provider)