Many iPhone X and iPhone 8/7/6 users are facing issue after upgrading to latest iOS 11.3 that while making calls speaker icon to change audio to speaker does not seem to be active and is greyed out completely. The pic here show an example of the same situation. Music and videos are fine through the iPhone speaker but the Voice memo not working.
This is very common habit of many iPhone users to turn on the speaker while on call but after the iOS 11.3 upgrade the speaker icon is completely greyed out. Many iPhone users tried to hard reset and restore their iphone from backup but nothing seems to help to fix the issue.
For many users the issue started to occur after using Bluetooth device with iPhone. One user of Apple forum quoted the issue as:
“My iphone 7plus has the same problem after updating to 11.3 last week.I connected my phone to Bluetooth earphone once, and after that my phone cannot make any calls. The speaker option is grey and cannot hear any sound.”
It seems that iOS 11.3 was working fine and calls were made with speaker option fine but after connecting the Bluetooth device the issue starts.
How to fix iPhone speaker option grayed out from call screen:
This seems to be hardware issue than software bug in iOS 11.3, please find a professional iPhone repair store and ask them to check the audio IC, it’s a tiny little chip on the mother board. For your idea iPhone 7 Plus audio IC will cost you around $60. If your iphone is still under warranty, please search help from Apple Store. If not, get the audio IC checked, and most likely it will work for you as well.