From what I have read hear previously in threads about this question and the fact that I haven't actually figured it out myself, I don't believe you can.
Now someone else can correct me if I am wrong, but monitoring my own SMS count through Verizon, I do not believe these msgs. count against you.
Whats weird to me is I have my SMS blocked and had no idea that it used SMS to notify about VM, good thing I still get the notifications. I just wish they would clear out after I check the VM as I need to do it manually.