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You can set the Anonymous Call Rejection using the PBX EndPoint Manager.
Go into End Point Manager in your PBX and select the Sangoma brand in the menu.
Click on the template in End Point Manager that you want to modify.
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Click on the Options menu tab at the top
Anonymous Call Rejection can be enabled or disabled. If enabled, all anonymous calls will be rejected and will not ring the phone. Some restricted callers will likely be rejected as well.
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You now need to update the phone configuration file. The three options at the bottom of the template are:
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