Complaint regarding faulty power bank purchased

I am writing to formally complain about a power bank I recently purchased from vodacom store for R200.

Before buying the item, I specifically asked how long it would last when fully charged. The sales assistant informed me that it would last for about a week. However, after purchasing and using the power bank, I discovered that it charges briefly and then switches off. It does not function as expected.

I returned to the store hoping for assistance, but I was told that because the device is not physically damaged, nothing could be done. I am disappointed because the product is clearly not working properly, and I believe I was misled about its performance.

I thought this matter will be resolved, either through a replacement or a refund💔💔💔💔🥺🥺😭😭