Have you tried logging in to the IRS website? Payment plan info should update in real time. Existing payment plans should show here:
Unless it's solved by using another browser (and disabling any popup blockers you may have), a visit to your local office may be your best bet unless you can perhaps get them to fax over a confirmation to you. In my experience, they like to use snail mail for pretty much everything, though, and that may not be timely enough.