Crisp lettuce sound

Owned this mattress for only 3 years, after paying over $800.00 for it on sale, and recently every time one of us rolls over, the mattress crunches like crisp lettuce and is loud enough to wake each other up. Since neither of us are overweight we know this is not a cause. Tried to reach the store we purchased it at in New Brunswick Canada(SleepZone). They appear to be out of business. We are not impressed and feel we have no local connection to turn to. We returned to Nova Scotia in 2010. I hope I am wrong and this issue gets resolved. Losing sleep is no fun at any time but when you have a 5am rise, its even worse. Also, the mattress used to feel supportive to my bad back, but lately I wake up with pains in my lower back and even my shoulders sometimes.