Incoming phone volume problem

I have a 2008 Prius. I use an iphone 6s with iOS 11.2.2

When I get an incoming call the volume is so low that I can not hear it.
Same with listening to voice messages.

I can quickly grab the phone go to the keypad and hit a button a number of times and the volume increases.

But I have to do that each time.

Did upgrading to the newer iOS have anything to do with this. Everything had been working just fine for the past 7 or 8 years!