Problems with the private messaging service

WM, mate I’ve tried sending you a private message about this, but I guess you didn’t get it.

I have now reached my limit of 50 messages in this service, but oddly enough, there aren’t any in there. I’ve deleted all bar a few that I really need, and those I’ve placed in sub folders. and been through the receipt messages and deleted those but it still says that I have 50. What can I do to correct this problem?