Can I use Outlook for contacts and calendar on my iphone ?

Simply add Outlook account on iOS mail app and enable Calendar (See the Pic at the Bottom for Calendar)

Settings > Calendar > Default Calendar [Choose Outlook, if you use often]. What you add (Event) on iPhone Calendar is synced with the default calendar unless you have chosen a specific calendar at the time of event creation.

Watch the GIF for Outlook and Exchange (Ignore delete portion)

Calendars (on iPhone)