Stop the ringtone

We use the latest stage caller with a airport express midi trigger by ableton.
the situation is we let ring a iPhone 5 like the actor is called on his phone.
we stop and start the ringtone by a midi note on and off.
last time the midi note off was not received and i was not able to stop the ringtone anymore, luckily the sample was not that long ore in a loop. pffff.
i can change that by stopping the ringtone if the actor touch the volume, but the danger is the volume will drop down.
It wood by so nice if its possible to stop the cue by push the home button. to avoid change volume.
Best Regards

To complete the information
macbook pro retina OSX 10.8.5
Ableton 9.2.3
airport express 802.11n
Midi over network by apple
iphone 5 iOS 9.1
Stagecaller 1.3.3

unfortunately I can override the home button (I think… I should check that) - I can disable it via what’s called ‘guided access’, but I don’t think that’s what you need

I can force set the device & action volume per action - and when the ‘emergency stop’ setting is on I could capture the volume change and reset the device volume… I’m not doing that currently - I run a few tests and see how that feels