Comment 12 for bug 1353379

As said, commercial networks do not support this feature around here. Voice mail message notification comes as regular sms message here. But you can trust that simulation works correctly. It has been used with several enough phones. Message going straight to the sim is a valid case.

And as said, it looks like that 255 is coming from using the card in different phone that updates the SIM differently. If that is wanted to be fixed I think easiest and quickest solution is stop reading file from the SIM. If we wish, we could enhance that solution by reading the value from messages. Third option is not to read the value before new voice mail message.

However, in my opinion this is a trivial case. After user checks the voice mails from network network should send new message that should update the count correctly. Problem with card that has been moved from one phone to another should therefore be shortlived.