15GB mysteriously used up in less than a day

[SarahS]

A few days ago, my monthly contract renewed, along with my data allowance for the month (15GB). However, the following morning I got a text saying that I was almost out of data and only had 2GB left. I called o2 and they confirmed this was the case but couldn’t help to identify why as they are unable to see my app usage due to privacy issues. In those (less than) 24 hours that my data was used up I didn’t download anything new or do anything different to usual, and was at home where I have wifi. Can someone help me work out what happened?

[MI5]

@SarahS 

All you can do is look in your phone settings under data usage to see which app(s) have used the data.

[SarahS]

I did and nothing was different than usual. No app was using up more data than it had in previous months. I feel scammed 😞

[MI5 · Accepted solution]

@SarahS 

I would suggest calling back and see if you get someone more helpful then.

Numbers here Guide: Coronavirus Community Help and Support 
Or advice from an O2 Guru regarding a way to get through:
If you call 202, when it comes to the reason you are calling stay silent for 15 seconds and you will be taken to the keypad options.
Press 2 for Everything Else
Press 5 for More Options
Press 7 for Anything Else which will put you though to someone.
Say "Upgrade", "Lost/Stolen" or "Fraud" if you have to, to get put through to someone.

[SarahS]

Appreciate that, thank you. I’ll call them again tomorrow

[MI5]

You're welcome and good luck @SarahS