So my mum recently called my iPhone, she uses a Samsung I think, and I was using it at time and was on the Skype app typing, but then she called at the same time and she said that her call stopped and a voice answer said that I was online or unavailable to pick up a call, but then she called again straight after and it went through. Is this true? If so how can this be turned off? If its locked she can call, and even if it's unlocked it rings, and I've tried it with my brother while it was locked and when I was using an app and it went through.
Depending on your carrier and the data connection used at the time a call comes in, it may not be possible to use both data and voice at the same time. This is a constraint imposed by the specific mobile protocol in use (Edge and GPRS for instance) and happens on all (smart)phones.