Amazon Ships Used Swan Dirt Master Floor Cleaner as New Item

Today I received a Swan Dirt Master Crossover three-in-one floor cleaner that I ordered from Amazon, and when I unpacked it I immediately noticed clear signs that the product had already been used. The water tank was dirty, there were visible water marks on the foot of the machine, and even the box had been resealed with clear tape rather than looking factory sealed. Because the cleaner arrived in this used condition, I do not know whether it works properly or if there are any hidden faults, and I do not feel comfortable using it. I am requesting a full refund for this order and would like clear instructions on how to return the product that was delivered to me in this unacceptable condition.