Why can't I hear calls from my smartwatch to my bluetooth headphones?

[AC Question]

I have a Samsung Gear S2 and a pair of Ecandy bluetooth headphones (And they do have a microphone). I can hear music and other sounds through it just fine. If I try to make a call, it immediately goes to my Gear. I went into the options during the call and the Bluetooth option is greyed out. I've had this problem with another set of headphones as well, and it's seriously beginning to irritate me. Can anyone please tell me how to fix it?