In most cases on your Telstra iPhone will be locked down and not allow you to edit the telstra.internet APN settings. If you can, the setting we want to change is 'APN Protocol' from 'IPv4/IPv6', to just 'IPv4'. This will restore video when on mobile data.
However if you cannot edit the settings of your telstra.internet APN, please follow this video to install an edited version of the telstra.internet APN. It is essentially the same with one small setting change, but allows full functionality of the DoorBird. The link to the alternate APN configuration is here... APN Configuration File *keep in mind this link needs to be opened from a browser on your smartphone for it to work. See the video.
Here is the video on how to install it: APN Installation Video