I don't know. But I did a Google search on "speedpay reviews illinois":
https://www.google.com/webhp?sourcei...views+illinois
Maybe one of these websites will give you some idea of how it works.
Edit: I just wanted to add that whenever I have had to make a payment via touchtone phone, I have always been given the option to confirm/verify the payment at the end. I do not think any telephone payment service could automatically charge your card without having you verify the amount and confirm that you want to make the payment. Have you tried it yet? Sometimes too you can dial and hit the * key to get a human operator so you can ask a question.
Edit 2: Sorry, some of those Google websites have speedpay only in their advertisements.
Here is information from one utility company that uses speedpay:
https://www.ameren.com/sites/aue/Arc...edpayORIG.aspx