I'm going to refuse to pay for a service I didn't ask for
What service are you refusing to pay for?
My ISP tried to charge me by upgrading my speed without telling me.
I get why you would not want to pay for that. I would not want to pay for it either.
I'm going to call them and complain and demand a refund.
I think that's a good idea! If they changed your plan and charged you more money without telling you then you should not have to pay that.