If the Bluetooth hearing aids are switched off, they will automatically disconnect from the paired device, such as the mobile phone. 

Other reasons for disconnecting from the phone:

• The hearing aid may have run out of battery
• Bluetooth is disabled on the phone
• The phone is out of range (10 m / 30 ft) from the hearing aids. If the hearing aids are disconnected because they were out of range, it may take up to 2 minutes until they reconnect.

The phone may be connected to another device (such as the car Bluetooth system).