There is no €12.00 plan.
I presume you mean that you bought a €12.99 membership plan?
What do you mean by you want it by Monday?
If you bought a membership plan then it will start when your current plan eventually expires or immediately if you don't have a current plan.
You can't start a new plan early if that's what you're asking about.
Why do you need it to start on Monday for your trip?
What does your Transactions page say about recent payments?
What does your My48 account Dashboard say about your current membership status and expiry date?
Does your Buy Plan page list any upcoming membership plan?
If you need to contact 48 support about this then see the links in my signature below.
