This article covers how to disable the voicemail in Teams, so that calls will ring through to the PBX voicemail or other Users in the call flow.
By default, Microsoft 365 Teams voicemail is enabled. Login to your Microsoft 365 portal as a global administrator and select the all admin centres tab on the left toolbar, followed by the Teams icon.
Select the voice drop-down and then calling policies. Select the default policy which is Global.
Locate the setting 'Voicemail is available for routing inbound calls', update this value to disabled.