I have 2 iPhones. A: iPhone 7 (primary phone) B: iPhone 6s (secondary/backup phone) Each has their own SIM card and assigned phone number and own data plan. If I set both phones to use iMessage linked to my iCloud account, can iPhone B be set to only send and receive messages from the phone number attached to iPhone A? I know it works when linked to an iPad or MacBook, but since iPhone B has its own number, I wasn't sure about this scenario. Thanks!