Shocked

I purchased an Intex mattress recently from outdoor warehouse at the West Coast branch Sunningdale. I recall asking the sales rep if they were 100% suited for 2 people and that they had no issues, returns as l have issues with my 1 hip, osteoarthritis. They confidently gave the thumbs up. Needless to say after my 1st camping trip...the mattress did not deliver( sinking in due to 2 peoples weight in the mid section)and l spent the 1st night getting all of maybe 2 hrs sleep and was forced to take anti inflammatory meds to ensure l didn't battle too much the 2nd night which slightly helped. My partner who has no hip or other issues, also said it was not great or ideal for 2 people. I took the mattress back to Outdoor warehouse and explained my situation and advised l want to exchange it for their firm flat mattresses, which now would cost me more, etc... to which l was met with a blunt rebuttal of we can only exchange if you have your box in which it was packaged. I explained l did not keep the box, but have the receipt and unfortunately can't keep any boxes due to lack of storage space. The assistant manager, was a very uncaring, incompassionate individual who wasn't at all worried about my actual complaint, and the more l reiterated its a medical issue, the more he bluntly referred to their policy. I eventually asked that he call a manager, which he did...and she proceeded to say the exact same. I then asked for the Regional managers contact number. The assistant...then took it upon himself to call this so called RM, never once offering me the phone to chat to him, but what seemed to be him trying to coerce his now seniors into following his biased flawed opinion as he returned eventually from the call ...simply saying the RM, said l must email them...and again was persistent in re mentioning the company policy and there's nothing they are willing to assist with. I said surely you can make exceptions for medical conditions( even advised l can a bring medical report) and all over a box??? I further explained l was about to purchase a new tent from them...but this entire experience has made me not want to spend 1 more cent in their store. I was absolutely shocked by their lack of customer care...not any stage was the assistant manager apologetic, compassionate or understanding in any way or form. So sad, this short sightedness...dont they realise its costing them customers and sales. I will not shop at another OUTDOOR WAREHOUSE again.