BAD SERVICE on PERSONAL LOAN

I was contacted by and ABSA representative to say that I have an outstanding loan account and I have to pay. When asked when this loan was taken out she said to me it was taken out in 1997. In the interim an collection company called DMC Collections (Blake & Associates) is calling me everyday about payment arrangements. I went to ABSA Northgate a week ago and they couldnt find the records of when the loan was taken out. The consultant then completed a document requesting the information because he did not have access to archive older than 10 years. I am still waiting on ABSA's responds. Blake and Associates calls me everyday about payments. I have on several occasions emailed them to say I will not pay this account until I have proof from ABSA when the loan was taken out. I found this very unprofessional from ABSA to say I have to pay the outstanding amount but they cannot provide proof when the loan was taken out.