Glad I found this thread, I thought I was losing it or that my iPhone 6 was trolling me. I didn't delete some old contacts so I managed to '*** dial' (phone was in my back pocket) my ex-girlfriend, an ex friend and a current friend while ordering coffee, walking home and listening to music and while riding a motorcycle.
I thought my headphones (Sony in-ear noise cancelling headphones seen in photo 3) were broken until I saw this thread. I'm currently using a Lifeproof frē case (link: http://www.lifeproof.com/shop/us_en/iphone-6-cases/iphone-6-case-fre/?color=Blac k+%2F+Black ) which has it's own adaptor for the headphones (seen in photo 1 + 2):
PHOTO 1) 
PHOTO 2)

PHOTO 3)

I read through and realised it's probably the jack which leaves me with two options: top using the Lifeproof case (not a good option as I have it for a reason) or cycle through different headphones (the expensive option and I can't really afford that) and see what's what. My only other headphones I can test with are the Apple headphones that came with my iPhone, and I hate them (they don't have noise reduction and the quality is bad in comparison).
Frustrating considering this same set of headphones seems to cause my phone calls to hang up randomly (even without voice control showing up) so it seems like I'm being forced to use Apple headphones if I don't want this issue.
Tested my phone with and without my Lifeproof case and it seems to be just using any non-Apple headphones. Frustrating as ****.