No response despite several calls

I purchased a bed (serta) from House and Home Centurion. I have attempted on several occasions since last week to report a problem as the mattress is sagging. Every time I have called I have been advised that somebody would call me back as the relevant personnel member was not available, had already left for the day, only comes in at 10 etc.. Needless to say I have not received the courtesy of a call back and am being frustrated in an attempt to get a simple issue resolved.