No sound during phone calls only
Hi, recently received an iPhone 6 from someone and they have had issues with the sound during phone calls. During a phone call the ear speaker does not work and the speaker button is dimmed and cannot be pressed. Also the head phone jack is not working. I know none of this is due to faulty parts as the speaker works fine on videos, I have tried a new ear speaker on it and I have replaced the headphone jack. There is no apparent water damage(markers are white). Have tried a hard reset (home and power button) tried a new sim, tried toggling the mute button during a phone call, have reset all settings (but not a full reset as I do not have iCloud password) and the phone is updated to latest iOS. Any thoughts what this could be? Any help would be much appreciated.
Also the phone might be from another country which might be the cause of the problem, however phone has reception and sends and receives texts fine.
Is this a good question?