Hi
You need to choose whether you want to configure the phone manually, or else to use 3CX Provisioning.
If you want to configure the phone manually, you need to remove the provisioning information from the 3CX Management Console.
If you want to use 3CX Provisioning, and you want this custom behaviour, then you need to look into creating your own custom template file for the task.
For details on this, ref: http://www.3cx.com/blog/voip-howto/phone-provisioning-complete-guide/