I'm the person who created my account and the only one who uses it - but I'm not the primary account holder?!

My service, which is supposed to be 50 mbps, has been getting ridiculously slow lately - downloads as low as 400 kbps - so I thought I'd take advantage of the "Upgrade My Modem" thing I keep getting ads for. Trying to access this, I get "Limited Access". Cox thinks I, who created the account four years ago, pays for it, and am the only one who ever uses it - am somehow *not* the primary account holder? What is this? Has my identity been stolen or something?