I just added admob ads to my app "Banner ads" and i notice its using more than 30MG i already searched for solution her in stack-overflow and other web sites and i didn't find any useful solution i already using the last SDK version and here is the version of ads library
compile 'com.google.android.gms:play-services-ads:11.8.0'
compile 'com.google.firebase:firebase-ads:11.8.0'
by the way i am using Kotlin . it's not duplicated because i already take look of the most of question and answers here and no one worked for me