Q: my wifes phone and mine get each others calls and messages

The best way is to get separate iCloud accounts. You can still share the content you want to by setting up Family Sharing (Family Sharing - Apple Support)

An alternative: What you are experiencing is a feature called Continuity. You can turn it off as follows:

• Settings/Phone: Turn off Calls on Other Devices on both phones
• Settings/Message: Send & Receive, check just the accounts you want on each phone
• Settings/Facetime: Check only the appropriate addresses on each phone