Galaxy Nexus (i9250) call issue

[bulkiera]

Owned a Galaxy Nexus (i9250) for 1.5 years and some more. Great phone but recently When I make a call, it would end up immediately in most cases. Have tired to remove the battery (currently a 5000mah of mpj), swapped back to stock battery, and reinserted the SIM card, but problem still happen. I am not very phone savvy, could anyone help me fixing it? Many thanks.