My mobile data wont stop getting used

Today and late yesterday I was getting notifications from my mobile data provider (circles) and it was saying i had used up 80% of my mobile data even though i was at home and the mobile data switch was off at the time. Ive been home since and ten minutes ago I got a notification saying I’d used 90% and i checked circles app and it was less than when i got the 80% notification. The setting mobile data said ‘off’ on the quick settings when you swipe down on the top right, and it said ‘off’ in settings. I have an iPhone 12 and I need advices