Poor service by RCS

I have one NWJ accounts with them, however two accounts appears on my Experian credit profile. I called disputed with Experian and they needed more documents which I don't have. I called RCS they confirmed that only one account is valid and they further explained that the other account which appears is old account which is closed. I requested a letter to confirm all what they were telling verbally. I was taken from Pillar to post, Is about a month even today I am still waiting for the letter. They really don't care about their clients. I am really disappointed by how my matters is handled. They are able to write urgent letter of demand if I fail to pay my account on time and they are unable to write a confirmation letter. The latest is that my matter has been escalated and it will take 24 hours. Just hope it will be real this time.