Using Prepaid Account Balance as Payment

I am an account owner/holder for a multi-line account that costs a total of $50 a month. My payment is due today and I do not have Autopay activated. I currently have an account balance of $53.50 which I would like to use as payment. When I signed into my account to make a payment, it says payment due is $0.00 and due date now. How can this be? Will the $50 just be taken out of my account balance even though I don't have Autopay? I hope someone can answer this for me. Thank you!