I fix iphones but I have never seen this problem before. Ive read a little bit about it online about resetting it while have the headphones in and then taking out while in a call. That did not work so I then proceeded to change the headphone/ volume flex cable because a lot of people were saying that could be the problem. Now it does not even work on speaker phone talking the customer has to use the apple headphones to make phone calls. Help will deffinately be appreciated in this situation.