Thanks for clarifying, bekaj74. Have you tried using any other headphones with the ThinkPad for making calls, to see if this issue persists? As the Bose headset is working perfectly with your phone, it'd be helpful to know how other headsets operate with the ThinkPad for reference.
Yes, other headphones work with it. I have my old pair of Bose QuietComfort 25 and they work fine. Although, these are wired and not Bluetooth.