FNB taking too long on an account query

Every month an amount goes off my account, and I have queried this for two months in a row now. It is a debit order to a Nedbank account, and Nedbank refuses to tell me who it is to. They say I must ask my bank, FNB. FNB never gets back to me to tell me the details of this debit order, and I don't want to cancel it in case it is a policy that the business has. My first reference is RD*** and the second reference is M***. I really need to know who is taking this money off my account. FNB have now \escalated"this query"