Black Stain inside my pots

What a disappointing experience I had with the most luxury pot brands. Am more hurt than angry so I bought 3 pots on sale last year in August but only started using m pots in October 2020, 8 months later the pots started reflecting a black stain in two of my pots and I was advised to buy the lecreuset pot cleaner which I did but still the stain remained. I took back the pots at the Brooklyn store and they took them in for assessment and hoping they will fix but I was told there is nothing wrong with the pots the black stain is where the enamel line curves. Wow I was shocked and I asked but when I bought this pot the line was not there and they said all our pots overtime do this and for such expensive pots that was not acceptable. Fast-forward I requested an exchange with a black enamel colour as I just recent also got a pot with a black enamel inside so I can avoid this black stain in the future caz it really doesn't look nice. they said its not possible the only thing they can do for me is give me a voucher o the value of my pots then I can buy but I got my pots on sale so the voucher will get me one pot not two has I had and its not my fault the stain cant be removed. We were up and down till I realised we not gonna a solution so I asked for a refund. then they ask for my bank details which I provided, when i make a follow up on the refund am now told I first need to go to the branch and sign papers before I get a refund. Something they should have told me before I asked about my refund but finally I got my refund and I will never buy this brand, to think it took me 3 years to save for this pots and I know many women who even go to an extent of doing stokvels to buy this pots. Am very disappointed shame.