What exactly does your online account say about your membership status and expiry date?
Does it also list a next membership and start date?
Remember that if you have a current membership and you buy a new membership (including data allowance) then the new membership stacks and does not kick in until the current membership has run its course and expires. In the meantime you cannot use the new membership allowances.
Buying a new membership does not prematurely terminate a current membership.
Membeships always run their full monthly course.
If you need a data allowance on a current membership then you need to buy an internet add-on.
Add-ons
Hope this helps.
