Unable to make outgoing calls
Make sure you have dialed a valid number and have touched 
.
For international calls, check the country and area codes.
Make sure your phone is connected to a network, and the network is not overloaded or unavailable.
Check your subscription status with your operator (credit, SIM card valid, etc.).
Make sure you have not barred outgoing calls.
Make sure that your phone is not in flight mode.
Unable to receive incoming calls
Make sure your phone is switched on and connected to a network (check for overloaded or unavailable network).
Check your subscription status with your operator (credit, SIM card valid, etc.).
Make sure you have not forwarded incoming calls.
Make sure that you have not barred certain calls.
Make sure that your phone is not in flight mode.
The caller’s name/number does not appear when a call is received
Check that you have subscribed to this service with your operator.
Your caller has concealed his/her name or number.
I cannot find my contacts
Make sure your SIM card is not broken.
Make sure your SIM card is inserted properly.
Import all contacts stored in SIM card to phone.
The sound quality of the calls is poor
You can adjust the volume during a call by pressing the Volume Up/ Down key.
Check the network strength 
.
Make sure that the receiver, connector or speaker on your phone is clean.
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