What shows you that the voicemail number is wrong? What happens when you try to access your voicemail? If you are seeing or hearing a specific error message, please let us know what it is.
What number is it showing? It should be +18056377243. When you attempt to call you voicemail does it not go through, or do you hear an error message?
Ya I thought it was a standard number - the one you posted is the same one I have.
Maybe it's different on an older sim card or maybe the OP was just confused when seeing that number and thought it was suppose to be their actual cell number.