I don't think you can do this with Global Capacity directly, but if the bill goes to a collection agency, it becomes easier. You just dispute the debt. Lots of pages online show how to do this and provide sample letters. You dispute the debt by sending a letter, then the debt collector has to respond within.. it was either 30 or 90 days. If they are unable to provide proof of the debt within that time, the debt goes away (because it's invalid).

You might be able to do the same with Global Capacity, but I think the majority of these rules apply specifically to debt collection agencies.