Colour failure

I bought a white shirt and a Black trouser at mr price using my account after 3weeks i noticed that the cokour of the trouser is coming off and my shirt is now turning black on the part where i tuck it in,i told them about that incident since September and they telling me to bring the slip i obviously don't have it anymore because i did not know that the colour will come off,and i boughy it using my account so they can check the account history and loom for that purchase i sent them pictures of the items and i am being ignored