Never received refund after mattress was returned

Our initial interaction with the company was great, but unfortunately the mattress didn't work out for my wife and I (it caused back pain). Our main issue, however, is the fact that the company has still not issued us a refund for the mattress we returned/donated, despite the fact that our refund was "approved" on May 18, 2018. We had multiple email, chat, and phone interactions where we were assured that we would receive our refund. However, we have not heard from the company again since July 2018 despite multiple attempts to contact them. We are still hoping that the company will honor their return policy and their approval of our $1299.99 for the mattress, but are unsure what to do at this point. (Unfortunately we didn't look more deeply into the company's reputation earlier because apparently they have many complaints against them that sound very similar to ours.)