Cannot turn off call forwarding

[BillinhoBamford]

When I do not answer a call, the call gets forwarded to a number that I know nothing about. I asked in my local O2 shop and they suggested calling ##002#, but this just gave a "Call forwarding Connection problem or invalid MMI code."

Can you please help me to turn this call forwarding off?

[jonsie · Accepted solution]

It can only be forwarding to voicemail

Guide: All you need to know about O2 Voicemail 901 

You will have to switch off wi calling on your account before you can use the code to cancel all diverts