Default voice line
Default voice line sim 1 and sim 2 own choice doesn’t not available options please give the option sim choose to call any person
iPhone 13, iOS 17
There is a difference between "Last Used" and "Always Use"
if you have selected a Line for a Contact, Say Line B as "Always Use"
and If that contact sends you a text using Line A then if you reply to that contact using the received message in the Message App as a continuation of the conversation then the Contact will be assigned as "Last Used"
Always start a conversation from the Contacts App if you want to keep Business and Personal lines separate.
If you start the conversation from the old thread then you cannot change it. Start a new conversation from Contacts App. Here you can change the number as well as the Line. As shown in the GIF below