You cannot imagine a smartphone without constant feed of Cellular and / or Wi-Fi data as many apps will stop functioning, rather stop responding, without constant flow of data. Same is true about Android devices.
But, on the other hand, it is necessary to keep a control on the background data to keep the bill of the Internet provider within your limits. Keeping this situation in view, Android has added a feature, as has been done in its many previous versions, to restrict the background data.
If you want to restrict background, you may do it but if you need any help, do see the instructions.
1: Tap the icon of the ‘Settings’ on the Home screen of your Android 5.0.2 Lollipop device to open up the ‘Settings’ screen.2: At the ‘Settings’ screen, tap the ‘Data usage’ in the ‘Wireless & networks’ section.3: At the ‘Data usage’ screen, tap the settings button, placed at the top right corner of the screen, immediately below the status bar. It will open up a popup menu.4: Tap the ‘Restrict background data’ in the popup menu. It will open up a prompt. 5: At the prompt, you will be warned that some apps and services may stop responding if you restrict background data and are not connected to the Wi-Fi. After reading the warning, if you are still willing to restrict background data, tap ‘OK’ and background will be restricted. 6: To know the current position of the notification, just tap the status bar and see a notification will be there, informing you, that you have restricted the background data. If you want to remove the restriction, just tap the notification and the background data restrictions will be removed.That’s all!