pathetic service

Nedbank gave me an overdraft 4 years ago, now all of a sudden they send my account to daly credit a fly by night unprofessional debt collector to block my cheque account because its in a negative balance caused by their overdraft that ive had for the past 4 years ..now i cant use my account , i have debit orders and i cant even get my salary , account is blocked , daly credit dont want to unblock it ...im inconvenienced .This is the worst service ive ever received from a bank .On top of that their call centre is clueless ..sending me from pillar to post.