High pitched screech with iPhone 6 Plus
Whenever I am talking to another person on an iPhone (I'm using an iPhone, too) I hear a high pitched screech like a fax machine. It can be heard by the person on the other end of the phone also. It only happens when calling another iPhone. I have tried to reset the phone, and restore the phone. No solution. Can I get some help?
Thanks
iPhone 6 Plus, iOS 8.1