bensons for beds wrong mattress delivered

mozzafan1

Bensons delivered a mattress to us recently. We order a medium connoisseur mattress. What we received was hard lumpy and nothing like the item that we ordered. We are unable to use the mattress and have had to sleep on a sofa bed. We returned to the store and spoke to a salesperson who told us to contact customers services by phone. We contacted customer support who were unable to help without an inspection first. A Fira inspection was carried out but the inspection was to determine damage. the inspector didn't have any way to compare the mattress to the one we should have received. Therefore his report will only indicate that the mattress is undamaged. Am I within my rights to return the mattress to the store and leave it to them to send a replacement to us.While in the store yesterday we took photos of the display models and have emailed them to customer services along with pics of the mattress we have been given. What is a reasonable time to wait for a replacement. We are currently using a sofa bed as the matress is unusable. Any help would be appreciated.
thanks