Generally if you are selling on Amazon, even if it's just reselling products from other people, you need to handle the customer service to a point.
Usually, the people buying the products are buying them from your store, and it does not matter that the product sourcing or fulfilment is done by someone else.
Ultimately these customers are your gold! Their level of happiness for their buying experience from your store has a direct impact on the likelihood of them buying from you again.
There's a thing we say that a customer is worth 10x more than a lead. Why? Because someone who has opened their wallet once with you is 10x more likely to do so again, provided you gave them a good customer experience.
Now, if you are just sending traffic to another person's store and earning a % for every purchase, that's a different story: then you have no responsibility for the customer.
[MORE TO COME ...]