HELP: Whatsapp Test Number added by mistake and can't be removed

I'm really hoping someone can help me with this. I was attempting to get my Whatsapp business number verified so I could send messages with the business name appearing instead of the phone number. It looks like I headed off down the wrong path and I did something with the Whatsapp API that added a Test Number to my Whatsapp. Now I can't find a way to remove the Test number and it also seems to preventing me adding a new number to the whatsapp manager.

Any help with this would be greatly appreciated.
Thank you