Hi Mamie,
Unfortunately you are in a difficult situation where you are locked into an exchange where there may be no good choices. Post #2 here includes some information and suggestions and links to threads with suggestions to other members who were in the same situation and some of the ideas that can help make the best of a bad situation.
The description of the mattress doesn’t include any information about the quality of the foams in the mattress but I can tell you that they are not good (in the range of 1.3 lbs density which is low quality).
If you let me know the store you are dealing with I’d be happy to take a look to see if they may have any reasonable options that may be worth considering.
Phoenix