In your first post you implied that you're using Avalara to handle your payments, but in your post above you just said that you're only using Authorize.net.

So ... which is it?

I don't know Avalara, so I assume they're doing the payment collection for you and handling your taxes magically, and thus nobody's doing any real payments via your actual website. And if that's the case, then you'll need to get whoever wrote the Avalara module to write it correctly so that it properly presents payment choices (EVEN IF IT'S JUST A GENERIC LINE OF TEXT THAT SAYS "Pay by credit card on next screen" if Avalara is handling payment after-the-fact.