Excessive data usage out of nowhere

This billing cycle, my husband and I ran out of data on our 10GB plan with 10 days left in our cycle. We have never, ever had this issue before. We normally have a few gigs to roll over.

We’ve both gone through and changed multiple settings. We’ve turned off Wi-Fi assist, disabled background app refreshing, and I’ve toggled a few apps to only use Wi-Fi. I also reset my network settings.

I still have apps pulling data in the background when I am not on Wi-Fi (drive to the store, etc). Pandora, Target, Weather and Music are the four that pulled data in the hour I was just out of the house, even without opening a single app on my phone! I am at my wits end. What else could be happening?