Checking Voicemail turns into three-way calling

Is anyone else having this issue? When I connect to voicemail (either by dialing *86 or by hitting the voicemail icon), I always end up with a three-way call with the third line being my passcode - which obviously isn't a valid phone number - so I get the anoying deedle-deedle indicating it can't be dialed - so I can't hear hte message being played..

Am I just doing something stupid? It just started happinenig in the past 2 weeks....