The Courier Guy online billing nightmare

Whereas The Courier Guy is good with actual delivery, their billing system is a total mess, putting my business in a bad position financially. Despite filling out all the details on the quote (size, weight etc), they bill you way more than you are quoted two thirds of the time. I have to waste my valuable time on fixing their errors, and I have to wait for my credit note for several days, or they argue with you when they are clearly in the wrong. In the meantime my account is frozen and I cannot book collections. Very poor online service.

My business is suffering. I cannot bill a client after TCG has overcharged me.