iPhone X

Good day, I have had my iPhone X for about 3 weeks... I have encountered so many problems with it, when I went to book it in... I asked them if the problem is with the handset can I please get a different colour... as I do not want the space grey anymore, they had said that they replace handset for handset... now I do not understand this, if they are replacing the entire phone why can’t they give me a different colour?