What do I do to get a debt deletion from my credit report?

I've sent a letter to the creditor asking for a deletion in exchange for a 80% settlement. I have not received any responses or reply and its been at least 30 days. How do I request validation of a debt or do I resubmit a letter to the original creditor. This debt is four years old, I don't even though where its from. It is a utility company.