O2

I think the wisest option would be to try and pay or setup a payment plan before it leaves o2.This can impact your credit file.

If you connected to wifi i would ensure wifi assist is turned off on the iphone.

More often than not if you havent paid your bill you will be barred, What happens if you call up and get it removed it will automatically go back on. You need to call customer service and get your account put on hold til you can pay it, Usually befor...

Maybe the direct debit bounce, Which then brought the balance forward but then you cleared it?Only thing i could thing off.