Technical Connection problem

[Alex217]

Hi guys, just registered for server and am having problems connecting, receiving the following error.

'This account needs need to be converted to a battle.net account' or it comes up with authorizing for a little while, then disconnects from server.

Any help appreciated :3

Edit: My MoP is 5.4.8 is there anyway to downgrade to 5.4.2 ?

Nevermind all sorted, swapped .exe