Thank you for your enquiry.
We are sorry to hear that you have a problem with your Sealy mattress and would advise that all mattresses will settle over time and there is an article here, which will provide some further information regarding the same.
We have a handy guide here for avoiding settlement in new mattresses.
If the settlement is really significant, ie a dip or sag where you believe the mattress spring unit has failed, it may be worth reviewing the contents of any guarantee provided at the time of purchase to see if there is any remedy available through that guarantee.
If you require any assistance with our products please give the office a call 0161 437 4419
We trust that this helps.