Not able to remove known bluetooth devices

I am setting up again PhoneAmego from my mac to my iPhone 4S to dial via bluetooth. It has worked before. I tried to pair my iPhone with my iMac. When I connect to my iMac it says "connected" in BlueTooth panel. But on my iMac screen it is asking to confirm the numbers for pairing. These numbers do not show up on my iphone so I can not confirm it. Then it says that pairing failed. On my iPhone it is not possible to connect to my iMac. And the iMac keeps popping up the pairing code and fails. I never get the confirmation on my iPhone

I have tried to remove my iMac from the device list on the iPhone but it is not possible to remove it or any other device from the list.

I have tried to turn off wifi since the iPhone connects also to iTunes with wifi for sync.

So how do I reset bluetooth devices on my iPhone, since I guess this would help?