Data usage types must be defined as refillable in order to be included in a refill data package; this is done in Admin Console.
To view usage types:
Access Admin Console > Data Management > Usage Types.

The Refillable Data column shows whether data is refillable or not.
To edit usage types:
Right-click the usage type you want to modify and select Edit to display the Edit Usage Type window.

Check the Refillable Data box to designate usage as refillable and click Save to continue.
Note
Be sure to indicate that the refill data is in bytes (TB, GB, MB or KB) because single occurrences (such as a text message) are not supported.