Thanks for the reply. I have tried both methods to end the call. and In both ways the same behavior is observed.
I believe that your reasoning is logical, since the issue appears only when the headset is connected, therefore I will try to connect a different headset and check the behavior, to rule out, or not, the headset.
Thank you again
EDIT: I have tried the same with another bluetooth headset (Jawbone Era) and the call ended almost instantly, so as projeto56 suggested it is related to the headset.
Thank you for the help