Just had my Alcatel IDOL 4S phone serviced at the Microsoft Store. After having a problem hearing with the headphones, I rebooted the phone but then ran into a problem with not hearing callers unless the headphones were used, or unless the phone was connected via Bluetooth... I was told there is a known bug with this phone where the telecoil option is turned on and prevents callers from being heard. He just went to Settings - Ease of access - More options, and turned Telecoil OFF. PROBLEM SOLVED... Also posted answer here: Why is it that my phone has no sounds?

Just had my Alcatel IDOL 4S phone serviced at the Microsoft Store. After having a problem hearing with the headphones, I rebooted the phone but then ran into a problem with not hearing callers unless the headphones were used, or unless the phone was connected via Bluetooth... I was told there is a known bug with this phone where the telecoil option is turned on and prevents callers from being heard. He just went to Settings - Ease of access - More options, and turned Telecoil OFF. PROBLEM SOLVED...