Headphone displayed all the time
The headphone display is on and i don’t have a headphone connected to the phone so i can’t hear anyone when making a call
The economical version of the Samsung Galaxy S4, released in July 2013.
Try the Chosen Solution in this link first to see if it resolves the problem.
I realize that it is not for your particular model phone but the principle is the same in testing and trying to fix it.
If it doesn’t work then here’s a link to the Samsung Galaxy S4 Mini Repair guide, which will allow you to gain access to the headphone socket so that it can be replaced, they cannot be repaired