Why are my headphones connected and sound is coming out from both the headphones and the speaker

[Android Central Question]

Ok, so I am using a tecno k7 nd today i was watching a movie and during the time a phone call came in, then my phone started malfunctioning, i couldn't answer the phone call if o tried so I let the call end by it's self, guessing the fact that the headphones were connected at the time of the call had something to do with the malfunction i disconnected the headphones immediately after rhe phone stopped ringing, the call came in again nd i picked it, after the phone call i connected my headphones back in and i noticed the movie sound was coming out from both the headphones and the phone's speakers. Other headphones work perfectly so this problem is only with this particular set
It's a 3 ringed jack set, and it was not cheap, please help

 

[belodion]

Did you plug them in fully?