Voicemail retrieval 083 100 no invalid

When you phone 083 100 to retrieve voicemail you get a message number not valid - this has been since 10 April. I called 808 and reported it and the operator there confirmed from her phones that it wasn't working although they (MTN) weren't aware of it. She said she would report it. It is still not working and I have had no feed back - unfortunately I didn't get a reference number.<br>