Hi KSL.
Welcome to our Mattress Forum. 
I am sorry to hear you’re having such a terrible time with your new memory foam mattress.
What is it about the memory foam that you and your wife are disliking?
To quote our wise Phoenix… Unfortunately there isn’t a completely effective way to “fix” or “firm up” a mattress where the comfort layers are too thick or soft without removing and replacing the materials inside the mattress because a topper will still follow and sink into the softer layers or any soft spots underneath them. Toppers can be an effective way to soften up a mattress that is too firm but are not nearly as effective a way to make a mattress that is too soft any firmer. There are a few suggestions in post #4 here that may be helpful but unfortunately in most cases a firmer topper will only provide a partial or temporary benefit and may introduce other issues as well (such as a sleeping surface that is too firm or that doesn’t contour as well to your body profile).
Is it not possible to exchange the mattress for a pillowtop model instead? It seems odd to me that they would have such a restricted return/exchange policy on such an expensive mattress. Would the trade in be for an entirely new mattress, or just firmer foam for the comfort layer?
NikkiTMU