No - you topup your cash credit balance first then text the number to buy membership with it being paid for from your cash credit balance.
I already posted to some relevant info here:
http://community.48months.ie/t5/Need-Help/help/m-p/34650#M12703
You can also buy membership in one go online using a bank card if you log into your My 48 account.
These key topics explain everything about topping up, membership, buying stuff etc.
How do I top up?
How do I buy stuff by text?
Everything about membership
Where has my credit gone?
Automatic membership renewal
Hope this helps.
