Poor advice & now stuck with a hard mattress

I bought the Forty Winks firm mattress (after exchanging a medium mattress within the 100 day policy) a year ago and unfortunately, this bed is now hard instead of firm. I like a firm mattress and was told to buy a firmer mattress as it would soften with time - this has not been the case. It is hard and now I wake up with aches and pains. When I went back to the store, they only asked for photos & a video to be sent to the main office for review, and then came back saying that they cannot detect any factory fault and it appears that the mattress is fine as is. I was given poor advice at the time of purchase (despite the good customer service from the store staff) and am now stuck with a hard bed which I am told to just get a topper (to spend more money on top of the *** I spent originally). When I went to a competing brand store, they immediately described my issue without hesitation knowing that the bed I chose would do that. I wish someone had told me and then I would have chosen differently. I will be going to one of your competitors from now on instead.