Karen loved to talk on her . She chatted with her friends, played , and watched videos. One day, her said, "Karen, our phone bill arrived , and it's much higher than usual. seems you've been using a lot data." Karen was surprised and a scared. Dad smiled kindly and said, "'s sit down together and look at bill. We can see which apps using the most data and find to reduce it." So, Karen and dad went through the bill carefully checked the settings of her phone. discovered that some apps were using in the background. Dad showed Karen to turn off background data for apps and use Wi-Fi when available.