What should I do if my data usage doubles unexpectedly?

We have 2 Apple mobiles both model 14 era, with an 2gb data contract a month (yes old fashioned but we are not young people doing lots of streaming and downloads). Over the last month we have seen a big increase in data usage. It’s been very consistent foe the previous 11 months (never beyond 4gb between the 2 phones) but in June we used nearly 8gb between us!

Coincidentally at the beginning of June, Sky our network provider reclaimed nearly 60gb from our Piggybank as they have changed their terms of contract, so data only sits there for 12 months rather than 36.

We had no prior notification of this happening which we are not happy about but Sky state they told all their customers. We believe they should tell us but there you go.

As we have not made any changes to our settings and what we use our phones for, we are at a loss to explain this massive hike in usage. Sky we’re unable to help although they have doubled our data at no extra charge.

Has anyone else encountered similar recent rises in data usage, or can anyone offer any explanation why this might have happened? We are ok with IT but far from experts on the workings of mobiles and data etc, please keep it simple!

[Re-Titled by Moderator]

Original Title: Increase in data usage