iPhone voicemail icon

[onyx39]

Just got myself a 4s on Three, and moved away from Orange.
I have set up my voicemail and it is telling me I have no messages, which is fine.
Problem is, I think I may have a voicemail that has ported over from Orange, again, not a problem, but how can I get rid of the new voicemail icon when I cannot access the "new" message?

[mrsimmers]

Leave your self a voicemail from another phone. Listen to it and delete and then the icon will dissappear.