Business Account contact change

We have a business account that was setup years ago, and need to change the mailing address and the point of contact.  How do you escalate this to get the proper assistance?  The normal customer service number is unable to help.  One of our engineers is assigned the phone, and if we try to setup online access it sends him a code in which we can't reach him when we need to download the bill.  How can I escalate to get assistance, he's frustrated as well!