Hi
gauravraja89,
Few things you can try:
Try swapping SIM's in different slots
Use Same SIM in different phone, use a different SIM in the same slot where vi is not working
Run SMMI test to check if hardware issue
Factory reset once
How to Enter SMMI_TEST (test hardware)
Go to Calculator=>type " .12345+= "
you will be entered to SMMI_TEST