Faulty device and they refuse to repair / replace !

I bought a Nespresso milk frother from the Nespreso boutique at V&A Waterfront. After using it for a week, I noticed some burnt milk patches on the surface of the container... strange, because I make a point of always washing this frother thoroughly immediately after every use. These patches were impossible to clean just a gentle swipe of a soft sponge, so naturally I had to use a bit of pressure in order to completely clean it off.

A few days later, the burnt mark came back and I then decided to take the device back to Nespresso. They refused to take it back because they could see hairline marks on the Teflon surface from the "Aggressive" cleaning that I did. They told me that I should've brought the device back uncleaned to proof that the device is faulty. This is simply gross ! There was no negotiation, once the device is somewhat "used", they take zero responsibility and won't even admit that there might be a manufacturing fault....

Nespresso is a big money making corporation... they will say/ do everything to ensure that they're always right... not the customer. By admitting that there could be a fault in their appliance would only mean that they will lose money.

All I wanted was an appliance in proper working order. I didn't demand a refund, I simply asked if they could repair it or replace it with one which is properly working.