Why can't I hear any calls on my phone unless I have it on speaker?
i have a BLU dual sim card advance 4.5 android 4.2.2
Welcome to MobiFAQ! Can you also hear others using wired or Bluetooth headsets? If so, then the earpiece speaker is probably broken. Contact Blu if it's still under warranty, or bring it to a repair shop.
There are two speakers in most phones, a loudspeaker, and an earpiece. If you can hear with the device on speakerphone but not when it is in regular mode, you most likely have a bad earpiece.