If a person has aspartame poisoning does simply quitting products that contain aspartame like diet soda treat the problem or is there other treatment?

No such thing: Aspartame can not poison you. This is based on a crazy web scam. There is no known toxicity proved with this product. There is some weak evidence that consumption of diet soda may be associated paradoxically with weight gain, in spite of the zero calories, but the reasons for this if confirmed are unclear and may be associated with eating habits in those who are soda drinkers.