Welcome to Using English, danialsolimany
The phrase "completely rather differently" is a bit odd.
A company sells two products: Product 1 and Product 2.
Product 1 has some customers, but they stop buying it, and don't buy anything from the company any longer.
Product 1 has some other customers, but they stop buying it and instead by Product 2.
The company treats these two groups of (former) customers of Product 1 differently.
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