Hi Williams198,
Thanks for coming back with an update on this. I'm very sorry the Account Number is blank on some of the documents from us. You can also find this on your Contract, which we would've sent via E-Mail, or post, depending on your billing method.
You'll find it on the right-hand side, under "Customer Account Number". Alternatively, you'll find this on your first bill, which you will receive within 14 days of your installation. If you're still unable to locate it via your Contract, I have also sent you a private message, so please drop me a reply up in the top-right, purple envelope and I'll see what else I can sort for you.
Thanks,