Pet Land Novi Selling puppies that have pre-exisiting conditions Novi, Michigan

My husband and I purchased a puppy from Pet Land in  12  Oaks Mall, Novi.  Apparently  our puppy was sick at the time  of  purchase but we were told  that she once had a cold  but was treated for the cold.  Not even three weeks later our puppy is sick.  I took  her to the vet only to be told that she possibly has pneumonia.  The only way for the vet to be sure is is we spend more money to have her xrayed.  If it is found that she has pneumonia it is our responsibility to have her treated.  Also if there is any other pre-existing condition/s we are still responsible for the bill.  After already spends a good deal  of money on her we feel as though Pet Land knew  that she was ill at the time of sale.  Also my husband tried to contact someone at the  store and they refused to speak with him.  Instead they gave him a number to  call.  My husband mentioned that the girl made a suspicious comment to him about him  bringing her back at the time  of sale and him getting $400 for her if he chose to do so.  She also mentioned  that they usually never offer that deal.  He asked her at the time of the statement "why then are they doing that for him?"  I don't remember what he said her response was, but now looking back  he  felt that the comment raised a  suspicion in him.  We are going to see what the store wants to do to make this right, but after reading  others reviews on the  store I'm not sure that they will.