Bad service

I'm very disappointed with the service from Lewis..I bought couches from them.they debit every month after I arrange for them to lower my installment.Now I see on my credit score it keep showing my score going down because Lewis flags me as missing premium every month. I escalated it to their head office.. a guy called me I explain him my storie and frustration. I Advise me someone will call me back with the matter. It's been a month I'm still waiting. Now credit score is so low I can't apply for anything else. I regret taking this couches I get statements which even shows the same amount I don't understand where my money is going to every month.