low call volume on iphone 6s after iOS 11.2.6 update

I bought the IPhone 6s about 2 years ago and after the iOS11.2.6 update I'm having the same issue with the volume during calls. The volume is very low when making or receiving calls, increasing the volume button doesn't help.

With every update there seems to be an issue. Updates prior to this messed up SIRI ( siri usually makes a sound indicating that it was listening and i could talk asking it to dial a number. The sound was missing with the earlier update and while driving I had to look at the screen to see if it was listening and it was to dangerous, its so pathetic) that issue is sorted out in the recent updates but the latest update messed up the volume during calls.