On Android, when I make a voice call to a C220 we have, there are a set of sliders that allow me to tweak the camera's microphone, and camera's speaker - and that's all fine as shown in the screenshot below. 

I've got an iPad too and when I load the Apple version of the Tapo app on that, there doesn't seem to be an equivalent way of setting the camera speaker volume.    The Volume button only changes the camera's microphone level. When you make a call, there is no option to do anything except turn the speaker off. 

Does anyone have any ideas? Thanks.