I am not sure how to do the watch thing but from what I have read to have two phones with Visible you need 2 different accounts which I think entails having two different emails addresses, I don't think billing addresses and using the same card matters. From what I have seen in the 15 months here they don't have an option for multiple lines on ones account. Best bet would be to contact customer service but lately that has been a nightmare with up to an hour or more wait time on chat. An FYI, chat took me 45 minutes wait time last Sunday. You can get a hold of them through Facebook Messenger or Twitter DM but I waited 5 days for a response on those.
Maybe another user has a better answer. One thing is you won't see someone from Visible here since this is a peer to peer forum. Hope you get an answer.
