PCWorld has a good report from an insider of why your ISP treats you so badly (Confessions of an ISP Customer Service Rep). The article covers a wider range of services than just Internet, but all the details can help you the next time you need to call a service rep and try to resolve a problem.
The recurring theme in the article, created by a real service rep in response to an earlier PCWorld article about hating their ISP, is that the person on the phone has little or no control over what they say and what they can do for you. In a few situations, they have some wiggle room and can be cajoled into helping you a bit more than the next person who calls. In other cases, idiot vice presidents have scripted their conversation and limited their ability to make customers, meaning you, happier.
In some cases, such as when you terminate their service, the provider actually plans to make you angry so you'll forget to ask them to waive fees like those for early termination. If you're mad enough to terminate, they likely dropped the service ball and have no justification to penalize you for leaving. But if you get angry at the person on the phone because they are under orders to be uncooperative, you'll forget to argue about the early bye-bye fees.
Never yell at or abuse the phone rep for two reasons. First, they may have no control over the garbage they're spewing, at least not if they want to keep their job. Second, they can write whatever they want to into your service record and you have no way of knowing what they write and no way to correct what they write.
Next time you get a real jerk of a phone tech on the line, and a small percentage of them are dimwits of the lowest order and obnoxious to boot, just hang up. Call back in one minute, and you'll get someone else. Don't yell. Be polite. Ask to move up the line to their supervisor, and ask that supervisor if they have the authority to do what you need done, like refund money or waive fees.
Don't yell at the poor phone rep, even if they deserve it. Your best bet for a positive solution is to get them on your side. Squeeze your stress ball, smile, and get your problem resolved.