Credit repair

Hi, I’m Kimberly and brand new to this community. I’m really looking forward to getting and maybe even giving some insight into needed situations. Today I’d like to know what to do with a credit situation. I bought some furniture in 2018 from a company that says it’s not like “rent to own” but it’s pretty darn close. I have a signed contract that states if for any reason I no longer want the furniture, to call them and they will take it back. I called told them I could no longer make the payments and I wanted to return the furniture. The lady said, “Oh, we don’t do that!” I went this route to start building my credit and I was in the 700’s. I called again because the next month my credit score went down. Same answer. I told them to come to get the furniture but they haven’t shown up for the last 1 1/2 years. Needless to say, my credit score has gone all the way to the 400’s. Is it possible to have all the negative reversed if I take legal action or will it just stay there because it can’t be changed.