Here's the short version of my question without having to read a novel:
I have Blue Cross Blue Shield of Tennessee. Doc said it was fine to take two vyvanse doses during the day, but she says my insurance won't cover the second dose. I know for a fact that she didn't confirm that with my insurance company. Can I just call my insurance company and directly ask if they will cover the second dose, or is that something only my doctor/their staff can do?

Here the little back story that goes with it:

I take 70 MG of Vyvanse in the morning and 20 mg of Adderal in the afternoon, but as of late, they've both become basically ineffective in helping my Inattentive ADHD (no hyperactivity). The Adderal is definitely not great, as it gives me some weird side effects that the Vyvanse doesn't (kind of makes me feel a little frantic, but not anxious, headaches, difficulty swallowing), but I need to take something at around noon every day, even though the Adderal is usually completely unnoticeable within an hour and a half of taking it. I've tried to take an extra Adderal in the afternoon, but it didn't do much to help and just gave me more side effects.
I've been interested in trading my afternoon Adderal for another Vyvanse. My doctor is okay with this, but has assured me that my insurance will not cover two doses of Vyvanse per day. But when I checked the drug coverage list for my insurance online, it lists Vyvanse as one without a quantity limit. I've mentioned this twice to my doc, but each time she casually mentioned that it wouldn't be covered and never actually check with my insurance. So my question is: Can I call my insurance company directly and ask if a second dose will be covered under my plan, or is that something that only my doctor/their staff can do? If I can call and ask and it turns out it can be covered, how do I get a confirmation of that so I can be completely positive when I tell my doctor?