See if you have a photo of it - taken before it was sent away.
Then quietly ring them up and explain what appears to have happened, record the time of the conversation and get the name of the person that you are dealing with, and then ask if they have accidentally sent you the wrong machine.
Use Please & Thank-you all the way, it pays divvies
If they say that they have sent you the correct machine, quietly, explain to them that you do not think that it's condition is acceptable and you wish to complain.
If their response is negative explain that you will be taking advice as to what your next steps should be from the local Consumer Advice Bureau.
Above all: Do not bluster or threaten, as it cuts no mustard and frequently gets one sidelined.