Poor service

I purchased I mattress from these guys for a child for is below the weight of 50kg and a few days later I have informed them that I am unhappy with the purchase and am willing to pay a cash difference for a lil better mattress as the springs in the mattress can be felt and is now a health risk to the child however when contacted the Phoenix branch they tell me they can't help me I can only use the mattress as a trade in, which is complete nonsense, the bed was barely used and it's still in the warranty, absolutely disappointing, will never recommend to anyone