Faded Black Pants from Mango

I bought a pair of black Mango pants, but they turned anthracite in four months, despite being washed inside out at 30°. I sent the product in for inspection, but the results were disappointing. Even market pants are of higher quality than this. Mango's after-sales service, particularly their warranty service, has left me extremely disappointed. I believe the problem with the pants is due to a manufacturing defect, and as such, I demand a free replacement or a full refund if that is not possible. Mango, as a well-known brand, should stand behind its products' quality and accept responsibility for defective items. I had high hopes for Mango, but the experience left me disappointed. I hope they address this issue as soon as possible and provide a satisfactory resolution to ensure customer satisfaction.