Bamboo bed

We've bought a bamboo platinum heavy duty queen size bed, the sides just flatten and you were lying on the springs, no support at all, so we contacted the place where we bought it and they did sent out a rof from Bamboo which give permission to swop the mattress. When we received the new mattress it was all the same story from the beginning, as a matter fact the new mattress is much more worse than the first one. Is there something we can do. I had 3 back operations and need something to support my back