Hello folks,

So I am from Pakistan and I just purchased the only 'Branded' guitar which is available here. Yamaha F310, I have been practicing on other china made acoustics and this is my first proper guitar. The problem that I am facing is that ever since I changed my strings from stock Yamaha strings to .10 gauge (now on .11) Daddario the "B" string won't stop buzzing, its hard to explain how it actually sounds like its not a proper buzz that you get when frets are uneven its more like ZZZ sound as if the string is vibrating excessively and is slightly touching some frets when strummed with medium force the buzz happens from 3rd to 7th fret and after that it improves. If I pick it gently It plays fine, and by gently I mean I can not play bar chords without this weird noise. Unfortunately there are no luthiers in Pakistan, the shop owners call themselves luthiers and they ruin the guitar further instead of fixing it so I am on my own. Here is what I have tried so far.

Current setup: .11 Gauge Daddario strings, action measured at 12th fret = 2.9 mm 

1) Bought a higher saddle to rule out saddle issues, raisied saddle does improve the situation but does not fix it, I would have made peace with this setup but the action is 3.8 MM with this new saddle and B string still makes this funny sound (just better than before)

2) B string does not make this sound when played open so I think it does not have anything to do with NUT But still I have tried placing some paper in the nut slot  to make it a bit higher and it does not affect buzzing at those frets.

3) I have checked fret level and they are leveled fine, not flat or anything.

4) Neck relief check, have tried straight neck, concave bow, Extreme concave bow (Improves slightly), Back bow...nothing helps.

3) I have tried raising action at both NUT and saddle at the same time and it does not fix the issue.

4) New strings: Initially I went to .10s but because of the buzz moved to .11s but still the same problem, I tried putting the stock strings back and the "B" string even on that set is buzzing.

5) Checked machine heads they are not loose. I am so pissed off that I can't track down the issue and there are no professionals here who could help me. I haven't played in days.

6) I havent tried .12 gauge strings but donot know if that will help either...I have almost given up on this guitar. Any help will be appreciated