Theres basically two types of pre-paid cards you can buy... Ones you have to register and ones you don't. The ones you don't register are more or less just like a universal gift card, good at most stores with plenty of restrictions too (like US only for example). The ones you have to register are accepted everywhere just like a real credit card. You buy a flimsy fake card from the store, register that on the net, then like 3 days later you get the actual card.
If you bought the kind you don't have to register then I don't think it will work with Attitude. If you tried WalMart's website tho, it probably would work. Too bad they don't sell the seeds you're trying to buy tho lol
I bought mine pre-paid from WalGreens and it was a Green Dot one. But honestly, its really not worth the trouble. I found out that registering the card includes all the personal info needed to get a real credit card - ssn for example. So, why pay the 10 dollar activation fee and 5 dollar a month charge for something that is exactly like a real credit card except prepaid? I canceled mine after making the purchase from Attitude, and plan on using my regular credit card next time.