wow full download client

Can you upgrade a wow trial account using a time card and using the downloaded fullgame?

I really would like to get a full wow account however i have the full client installed right now however the problem is If i just buy a time card like what i want to do when i look at my battle.net account to update it it seems like id either have to pay 20 bucks to upgrade it online or get the disks. However id rather just buy the time card at wal-mart. Any idea would be well appreciated i really don’t want to put this on a credit card though.
I was expecting what mr baconbits said If the game comes the 30 free days I might get it then.

You need to buy the game, the original wow comes with 1 month free of wow. That would be your best bet, cause each CD has a CD key, in which you need to upgrade, you can go to walmart and buy the discs, upgrade to WoW and then throw the discs away, all you need is the CD key.

MenaceScape – Download Client