Note that speed dials on the device are not overwritten even if you don't disable provisioning...
Unless something has changed in the past few days, that's contrary to everyone else's experience and what's documented in the OBi Device Administration Guide:
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Speed Dialing of 99 OBi Endpoints or Numbers
The OBi device supports Speed Dialing of 99 numbers. These numbers can be associated with phones reachable via an Internet or landline service or the OBiTALK network. Be careful with the Speed Dial Set-Up as this will conflict with the Speed Dials set-up on the OBiTALK portal. The Speed Dials that are set-up on the OBiTALK portal will always overwrite anything set-up via the phone connected to the OBi.
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∞ Note: Be careful with the Speed Dial Set-Up as this will conflict with the Speed Dials set-up on the OBiTALK portal. The Speed Dials that are set-up on the OBiTALK portal will always overwrite anything set-up via the phone connected to the OBi.