Why do you need to if you're on the €12.99 unlimited data plan?
Or are you on one of the cheaper legacy plans with a limited data allowance?
And you've used up your membership plan data allowance and bredea data add-on in order to use mobile data until the end of the membership month?
What happens when you try to buy a data add-on?
Any error messages?
When were you last able to successfully buy stuff on 48?
Is your payment card still valid, not frozen via your online banking, and there are sufficient funds to cover the payment if it's a debit card?
If you need to contact 48 support about this then see the links in my signature below.
