When you get a new phone you'll want to make sure that all your contacts move over. You should store all contacts in the Outlook app on your phone and the People app in Office 365 - these will then sync with each other so you can access all your contacts from any Internet connected device.
The attached article shows you how to set up sync in the Outlook app on your smartphone and also suggests a solution for moving contacts from the 'Contacts' app on your old phone if you've used this previously.