Unable to cancel a prepaid card

Dear Visa I realised 3 months ago that I had a prepaid card that expired sometime ago and where I have a credit balance. After visiting 3 Nedbank branches, waiting in queues and trying to explain what I needed, I was referred to the Call Centre. I have made numerous calls and have been transferred from pillar to post but nobody has been able to assist me there either. Very frustrating to say the least. All I want to do is transfer the credit balance to a current account and cancel this card. Please advise if this is impossible or whether someone can assist me please. Thank you MG Valenti