If you purchased the Battlechest digitally from Blizzard it can take up to 72 hrs for it to be activated.

I just had this happen upgrading 3 accounts to MoP. The accounts showed the upgrade in the account section of the website yet when I logged in to WoW I still showed trial accounts. If you look at the transaction section of your account on the website it will show "queued" next to the purchase.