Sometimes, some phones, including iPhone, behave oddly with Bluetooth headsets. The headset will indicate an incoming call, and the user will push the button to accept. The device accepts the call, however, for some users in some circumstances, their mobile phone takes priority for the call and "steals" the audio from the headset and handles it via the handset instead.
If possible, you should check about having the Bluetooth headset paired with a different mobile phone to see if the same phenomenon occurs with it. If not, you may wish to consult the phone's manufacturer for assistance.
answered 1 year, 6 months ago