What does your My48 account Dashboard say about your data balance?
48 don't track your data usage (e.g. by app/service) so you need to do this yourself on your phone.
Most phones have some form of built-in data monitor but there are also lots of free and paid apps for doing this and figuring out what apps/services are using most of your data allowance.
If you were previously using c. 80GB per month then it's only a c. 20% increase to using the full 100GB.
In that case you might want to consider buying the €12.99 membership plan which comes with 200GB.