My iPhone automatically changes the audio level to max/zero

Thanks for the info. But it doesn't offer any info about my problem. It's only about speaker which I never had a problem with. Just the "restarting the iPhone" step is somewhat useful, I already mentioned that. I guess I have to restart my iPhone all the time when it happens

This problem became much more frequent this week, up to 3 times/day. Is there really no solution for this problem? Should I take it to the place where I bought, to make the personnel send the iPhone to repair shop?

I wanted to update this post. I realised a something new with the issue and found a way that I can temporarily solve it without restarting the iPhone. Right before it happens, an orange blinking light appears on the empty (white) side of the sound level at the music player. I marked that area on the photo below, although I couldn't managed to capture that orange blinking light. If I change the sound level via buttons, sound goes to max or min (depending on my button choice). Unplugging and re-plugging headphones don't affect this. After re-plugging, blinking continues. But if I unplug my headphone, then close the music player from double tapping the home button & restarting the music player, turns it it to normal. Even my sound level stays the same, at the level I configured before this issue starts happening.

A remainder, this issue only happens after I start listening to music with my headphones. Same thing with speaker never happened. I hope this message make you all understand my issue better. I also hope that there is a solution

I've finally managed to capture that blinking light. Here's photo. And I still couldn't find a solution for my problem.

http://imgur.com/oBNlM1K

small edit: I haven't updated my iPhone to 8.2 yet. If the update is to solve my problem, I'll update my iPhone

I had my iPhone 6 plus changed last week and restored to the lastest backup. The issue still continues