Why my iPhone 6 is using speaker by default for all incoming calls fix

The issue is with iphone 6 and above with iOS8 onward that every time the users tries to make or receive a call from his/her iphone then call automatically goes to loudspeaker. User will have to turned it off during a call manually, but for the next call the same problem persists:

How to fix iphone loudspeaker call issue:
First lets see "why iphone uses speaker to answer the calls"

Actullay the iPhone starts speaker while on call if user ear is far away from it, which is controlled by proximity sensor. If it detects that the iphone(which has a call) is not near to the ear, it would start the speaker for the call. Sometimes this happens when you push the earpiece even a little bit out of its range; therefore you have to place it close or on your ear.

If you find this feature annoying you can turn of the feature by following these steps to turn off the settings. with IOS 8.1.3
Go to Setting/General/Accesibility/Interaction/Call Audio Routing/Set to Headset not Automatic or speaker. After this restart your iphone and check the issue.