Bed sinking in and it’s been rotated monthly as you recommended

My name is Millicent I bought a bed restonic Bali last year on the 14 of October in January this year noticed the bed sinking in and decided to inform the store in sky city of the problem they logged they query on my behalf with the supplier res tonic and was requested to send pictures of which I did feedback was not provided I then went back to the store was told need to rotate the bed every month they won’t refund/exchange am not happy with the bed it’s I hardly a year and the bed still sink in regardless of it being rotated,I will really appreciate if sleepmasters could assist with refund or exchange am not happy at all