Good morning all,
I had this same issue with my iPhone 7 Plus. My speaker button was ghosted out during a phone call, I couldn’t hear anything during a phone call, no one could hear me during a phone call, but I could talk through a Bluetooth device (such as my car radio). I went to my local AT&T store where they suggested I go to the Apple store to see about fixing the problem or upgrade my device in their store. I did neither and resorted to this blog. The comments gave me good advice and I soft reset my phone by holding my lock screen and volume down button for a few seconds. Each time I performed the soft reset, I tested my phone by making a call. I had to soft reset 3 times then my phone started working again, saving me $700+.
Thank you to all!