I am being charged the wrong amount every month

I have Internet More and have set up autopay through my bank account.  I have spent hours on the AI chatbot and with live agent and still the billing is wrong.  I know the base charge is $40/month for my 300MB service, but I was told autopay gives $5/month discount if by credit/debit card and another $5/month if by direct bank draft.  So I should be charged $30/month, but am being charged $40/month.

This was verified in every chat seesion I've had, and with every live agent I talked with.  Now how do I get the billing system to credit my account for the $10 current month overcharge, and make sure I get billed only $30/month going forward?

Thank you for some help!