You don't need to delete the Duo account on your current phone, just add the new slide.
In fact, I don't think this would even be a question for the Meraki community. See this guide.
https://guide.duo.com/add-device
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.