You posted about the same issue last year and I replied to you then - the same answer that I posted at that time still applies:
If you've used up your data allowance with a few days still left to run on the membership plan month then you'll need to buy a data add-on to continue using mobile data for the rest of the membership plan month.
If you're habitually running out of data before the membership month is up then you might want to consider switching to the €12.99 membership plan which comes with unlimited mobile data.
If you need to contact 48 support about this then see the links in my signature below.
