( Head phone symbol appears on display without connecting head phones)
This symptom in cell phones occurs with bad head phone connector or its related circuit. Usually Speaker and micro phone circuit will have separate circuit path in any cell phone. These two circuits will have relation in head phone circuit only.
The technical reason is, when head phones pin is inserted into cell phone head phone socket, You will observe head phone symbol or car symbol (in some cell phones) on the display area of cell phone, also you can observe the internal speaker and internal mic will be off, same time external speakers (in the head phones) and external mic ( in the head phones wire) are activated.
This is because of head set detector contact on the circuit board which will be activated when head phone pin is inserted. You can see in the above picture, the circled areas, the disconnection mechanism inside the head phone connector when head phones pin inserted.
Most of the cases the Head phone socket of cell phone will be bad. Very few cases the circuit related to this is faulty.
Insert and remove the head phone pin 4,5 times into the head phone socket, with which you can have connection inside again.
If problem not solved , consult a qualified cell phone technician to change the head phones connector or for circuit board repair.