Exchange Online Contact sync with Android

Hi, 

We are using Exchange Online as our email platform in our organization. We use Outlook for Android clients in mobiles. Email and calendar is syncing fine, but update done in contact take long time to appear in the mobile device. Why Outlook does not have its own contact folder in Outlook for Android program. It sync contact to the native contact folder in Android. Sync Contacts is already enabled under settings of Outlook profile. If I add a contact to outlook  in my Computer, it does not appear in Android mobile for few hours. I tried the pressing Sync Contacts under Android Native Contacts program, no luck, How does this Sync works, at what frequency or schedule this occurs? How can I force it to sync?

Thanks

Charles