Have you disabled auto provisioning (System Management > Auto Provisioning > ITSP Provisioning > Method - Disabled)? If you're going to change the settings directly on the OBi device, you need to disable auto provisioning; otherwise, your changes will be overwritten by the configuration retrieved from OBi's server (i.e. the configuration modified through the OBiTALK portal).
Alternately, you could provision your device for Callcentric through the OBiTALK portal and leave auto provisioning enabled.