Sleepmasters Faulty bed refuse to exchange

Bought a faulty bed. Reported it in a month because I was not available to use the bed. I’m still sitting with a wrapped faulty bed, it’s been 4 months and sleepmaster refuses to act. They have not even called me I keep going back to the store to get feedback with my complaint. They telling me I took too long to report after purchase. What happened to the guarantee and normal procedure for reporting a dispute. I feel ****med especially since I was not considering buying a bed there and fell for the marketing. I’m so angry I can’t believe this is coming from sleepmasters. What do I do with a broken or faulty bed