I've had them call late (never on time) and once when it was an hour late I rang the receptionist to say I thought they'd forgotten me, and a different doctor called back, so chase them if it gets really late? I panicked the first time because the app did the same.
It's mostly just annoying - the hospital have always called me on time, but the GP stress you out, because you're convinced they've just skipped you. And once the doctor rang for two rings and there was no way I could answer in time, and refused to call back.
msdawnfoster@gmail.com Tusk is the best Fleetwood Mac album. Only care about LFC.