Facetime on iphone 4 not working

Right I hope this is in the correct place.

When using my Iphone 4 to call the facetime on my Imac it always says my user is busy and for call back later, but whe calling from facetime to iphone it works ok anyone have come trough this problem and know what the solution is?

I had this problem for a short while, and for me the answer was to give each device a TOTALLY different address on which to reach it by FaceTime. So for my iPhone, I use the phone number as the FaceTime address, for the iPad I use an email address. Could have also just given each device two different email addresses.

If your devices have the same address listed for FaceTime (even if its just an alternate), it's like trying to call another phone in your house.

Thanks for answer I'll give it a go.

But if anyone know any other solution please post it, cause it used to work just fine before.