Can I exchange my IPhone 8 case for a new one?

I’m writing this in order to complain about a product I bought for myself and for a friend of mine as a gift at your store in October last year.

I have always purchased Apple products and have never had problems. However, the 2 IPHONE 8 cases I got last year, that is, 6 months ago, have been spoiled. They have also had stains on them, etc.

How could I have the problem concerning the 2 cases solved, please?

2 cases:

Tech21 Evo Elite iPhone 7P Rose Gold

Part Number:

I’m looking forward to hearing from you very soon.

Sincerely,

Alessandra Bautista da Costa