If you face unusually low calling volumes or have issues dialing numbers from your phone, you might be a victim of bugging. When a phone is being used as a bugging device, it has to transmit the incoming audio to a 3rd party, for which it utilizes the same pathway you use to dial numbers and make voice calls. When the two data streams compete for space, you get errors, dropped calls and bad call quality. However, with faster data networks, this has become quite rare because networks with high speeds are able to transfer multiple streams without any issues.
You should be monitoring your phone’s battery use throughout the day. If you are running out of battery unusually fast, it is possible that an app is working in the background or that your phone is constantly being used, even when you lock the screen. If you have not installed any applications lately and your battery is being drained faster, your phone might be monitored.
When your phone’s screen is locked and switched off, it is not supposed to be working in the background. However, if you pick up your phone after some time and it feels warm to the touch, it indicates that it was not shut down properly and was in use even when the screen was off. This can mean your phone is being used as a bugging device.