Twin xl mattress (Bay and slater st)

12 inch gel infused memory foam mattress. The description said it was firm. But not firm enough. Bought on July 9. Slept on twice. Just got my refund and I need to dispose or donate the mattress. Pick up only. I do have a dog so not sure if that would be a problem for someone with dog allergy. Non smoking.
I included screenshot of the ad