Hi,
I have used QT but not on maemo, so my answer would not be maemo specific.
Looks like the problem is that your QLabel object is created on the stack and destroyed after the slot returns. so what you should do is create the QLabel as a datamember of MyClass and create it in the MyClass contructor. Use the same QLabel in main and in the MyClass::receiveCall() slot.

hope this helps.