Zte Grand X User Manual page 61

To configure your phone to receive Internet calls:
By default, your phone is configured to make Internet calls, but
not to ensure that you will receive them. But you can configure
your phone to listen for Internet calls made to an Internet calling
account you added to your phone.
1. Touch the Home Key > Menu Key > System settings >
Call settings > Accounts.
2. Tick the Receive incoming calls check box. Checking this
setting will reduce your battery life between charges.
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