If multiple attempts at degaussing the monitor (a bulk tape eraser does a great job, but keep it at least 3" away, and turn it on or off only when it's at least 6 feet away) don't clear up the uneven color, then the "beam landing" wasn't adjusted right at the factory. This used to be done on Sonys by placing small magnets around the yoke (electromagnet near rear of picture tube) and front perimeter of the tube, but it's possible that there are built-in digital adjustments accessible through a service menu (secret combination of button pressings may bring it up) or a special serial connection made just for service.
I suspect that you didn't speak with a real technician because even slightly trained people in tech support are now often referred to as a "technicians," and some are even called "engineers." One Panasonic support "technician" even told me, "I don't know what convergence are," and he suggested that the serial link for service was through pin 8 of the video connector, an impossibility because it's for blue video.
If you just want to foul up the picture badly, try unplugging the monitor overnight, then move the yoke around and, if they're not sealed with paint or glue, move one of the tabs on the ring magnets at the rear of the tube. There are ways to ruin the monitor, but they're dangerous because they require shorting out certain parts, such as the circuit board on the back of the picture tube, the flyback, or one of the big chips or transistors. Don't do any of this while the monitor is powered on, and be sure to remove the shorts after the damage is done.
I think it would be better for you to protest to your credit card bank in writing to the special address for complaints because that gives very strong consumer protection and requires the bank to act on your behalf or refund the money. Also try PC World magazine's "Consumer Advocate" column.