Change primary email address

I have called customer service 6 separate times to get my primary email address changed.  Each time I get passed around from CS, to web tech support to another tech support to finally someone who claims they can make the change.  They always tell me it takes 48 hours for the change to reflect on the website.  It has been three months since I started requesting this change, the last call was about three weeks ago.  Sadly, the email is still unchanged.  Please help.  The old email address is no longer valid and I would like to receive electronic bills. This will be my last attempt to get this resolved.  I will be forced to rely on paper if it is impossible to change the primary email address.  Thank you.