Hi
You sure can buy Internet add-on 1G=€3.
Also, you need an active membership running too...
Im not entirely sure if you use all of your internet say, The Don's 5G allowance, if you may be
on 48's fair usage/suspension radar...but, then - see this below.
"Inclusive Membership Allowances: Your inclusive membership allowance will expire when your active monthly membership expires or when you have used your inclusive allowance, whichever should occur first. Should you use your inclusive allowance before your active membership has expired we will notify you and you will be able to purchase additional add-ons"
I would be very aware of my internet usage in this case, & i would heed any initial fair usage warnings.
I hope this answers your question adequately.
🙂