Absolutely useless their customer service.
Can you read somewhere you have to return you item to China? No! You can't do it anywhere because it's not written anywhere.
But....you will know about that when you sent back your item ( the return address you can find on your track label ). You will know it would not return address!!!, they didn’t receive anything from you ( does not matter you have all the evidence from Royal Mail, they don't know who is Marting).
Be careful to buy something with this company.
They will take your money and you never seen them !
Be careful!