- Check the signal strength on the phone screen, and move to an area with better reception. If you continuously experience low signal strength in a certain area, the network coverage may be insufficient there. For more info, contact your network operator.
- Remove any accessory covers or shells from the phone temporarily to check if they affect the signal strength.
- Set your phone to use GSM (2G) network only: Select Settings > Phone > Network mode > GSM in case the operator does not permit you to use 3G service (not available on some phones).
- Switch off your phone and take out the SIM card. If the SIM card is not properly inserted or the SIM tray is not fully closed, the phone may get disconnected from the cellular network.
- Put your SIM card in another phone to check if the issue is with your phone or your SIM card.
If your phone has two SIM cards, while one SIM card is making a call, for example, the other is unavailable and so its signal bar disappears.