Plugging in 3.5mm headphones randomly calls my last contact

[tracerit]

i've been bringing my phone to the gym and listening to music and i've noticed after i plug the headphones into the 3.5mm jack it'll randomly at times call the last number dialed/call i received. i have to end up turning the Phone feature off (Airplane Mode on basically) to avoid embarrassing calls.

I even have Voice Command off.