trying to activate a new mini box, and when calling the number, it asks for a phone number associated with the account. given them every number that could possibly be and nothing

Give them the account number on your bill.

Normally the automation doesn't ask for a telephone number but a PIN.  You may have to set in your Cox online account.

I would call cox communications, and speak to the operator, you can usually press 0 and be connected to a human.