Dial a bed = Dial a nightmare!!!

I bought a Simmons Firm mattress in February 2019.when I chose the mattress it seemed to be fit for me. I paid over 14k on a special deal they apparently had running. After sleeping on it I found it way too firm and had immense difficulty falling asleep and pain in my hips and lower back. Obviously the mattress was too firm. I contacted the outlet in George and asked too swop it for a medium firm. I was told they won't take it back unless I pay in an addisional 6k... I feel I'm been ********** as a consumer. Since Feb I have spend a total of 6 nights trying to sleep on this mattress. I've been sleeping in the spare bedroom on my old Mattress Shop mattress only having to look at this 14k I threw in the water. Dial a bed = Dial a nightmare.