iPhone 7 random volume drop and increase

Ive had my iPhone 7 for about 5 months now and recently it started to do a some weird things.

I was listening to some music on it when all of a sudden the volume drops to zero.
I would push it back up but it would go back down again.
It is like as if someone is holding down the volume rocker.
I would try to push it back up, but it keeps on forcing itself down.

The problem goes away in few seconds, but comes back randomly without any specific reason.
It doesnt matter if Im listening to music or watching a movie or etc.
The system would just rocker the sound down NOT my ringer volume though.
In settings, my volume rocker is set to adjust ringer volume so it shouldnt be like a connection problem there.

Now this was few days ago, now its started to do things oppositely.
It would always raise my volume for some reason. No matter how much I rocker it down.
Now today, it sets the volume to "3".
I always keep my speaker to 0. But it would just raise it in the background.
If Im like watching a twitter video without sound, it would just raise all of a sudden.
It even raises itself in the background so I would keep it at 0, but the next time I open a video or something, it would be set to 3.

Obviously its not volume limit in settings, Apple Support was unable to help me.
Im trying to fix this on my own if its possible since I dont want a refurbished iPhone for replacement...
But if its necessary I will.

This occurs on both headphones and speaker.

Anyone having a same issue?
Did you come up with a solution or anything?

 

I did and that didnt seem to work.
I would try once more but my MBP 17 just died last night due to logic board failure.

I called AC and they told me if its not a fixable problem they would replace my iPhone but not brand new, a refurbished iPhone by Apple.
They said they'll give me a new iPhone. But I wasnt sure if its really brand new so I asked they specifically and they told me it will be a refurbished model.

 

I was worried about refurbished since I was once told they use refurbished models on devices they cant find a problem with.
Problems similar to mine, when you dont know when it will occur and they cant find the problem (even though there is, its just that it occurs randomly), they'll stick it right into the refurbished models.
I dont want to go through another hassle because it was a refurb iPhone lol

 

That is actually quite impressive and great to hear.
My iPhone was also purchased on launch date and so far hadnt had any problems except my current one.
Iam in AppleCare+ so I should be able to have a free replacement if its a faulty device for the next year and half at least...

 

I had also guessed that. Tried without a case for about a day but no use.
The case Im using is a Spigen Ultra Hybrid.