@herlek: Do have a comment to this subject? Thanks.
I don't have any idea what is the reason. I made some research and changing the following registry settings could solve your problem.
[HKEY_LOCAL_MACHINE\Security\ECallWithoutSIM]
"List"=multi_sz:"08","000","110","112","118","119","911","*911","#911","999"
[HKEY_LOCAL_MACHINE\Security\ECallWithSIM]
"List"=multi_sz:"110","112","119","911","*911","#911","999"
I think if you remove the 999 it could do the trick, but you have to test it out yourself as I moved already to my next Phone. I can't do any testing anymore.
edit1 : please post your finding after testing. Not quiet smart for your provider to use emergency Phone number as number for voice mail???? (First introduced in the London area on 30 June 1937, the UK's 999 number is the world's oldest emergency call service.) Are you sure you dial the correct number for voice mail - usualy it is a 4 digit number NOT a 3 digit number.