How can I provision one IP Phone with single MAC address with Two extensions on it. If the MAC has been provisioned, then same cannot be provisioned against a different extension on same IP Phone.
Eventhough you can register mutlple extensions on a single IP Phone, You can only set up one extension using a single MAC address. The second extension that you register will always be shown as UNPROVISIONED as there is no MAC address associated with it.
We do not support multiple extensions on deskphones. It may work if you do it manually but you may face compatibility issues as this is a scenario that is unsupported/untested by 3CX.
The only phone devices on which we officially support multiple accounts are under the FXS/DECT category.