Hi there,
Thank you for reaching out to us.
If you are referring to disabling banner ads that are currently being shown (given that it's normally only banner ads that are being constantly shown to a user), then you may call a banner ad's AdView.destroy function in order to properly disable it. With that said, I would also recommend not initializing the AdMob SDK in the first place if the user's choice (of not displaying ads) could be retrieved at the start of your app, in order to prevent unnecessary memory usage.
Regards,
Ziv Yves Sanchez
Mobile Ads SDK Team