The in-game shop is available for the Classic client, which includes Era, Hardcore and SoD realms. We do not have the ability to disable the shop on specific realms.
We have an FAQ that you can open directly from the game (if you mouseover the Character transfer option, you’ll have the description), which then provides more information.
If you purchased a Character transfer and are unable to use it, you can request a refund from the website directly:
https://battle.net/support/help/product/services/334/1997/solution