Mobile authentication doesn't work at Nedbank

Every time I want to make a payment online to a new person, I have to call the service center to assist with my mobile authentication - I spoke to a lady briefly who then put me on hold - 12 minutes later I hung up. Nedbank charges me what I consider to be a lot in bank charges but somehow seems unable to make the mobile authentication work - I receive the message but it doesn't go back to them. When I call, I spend the better part of half an hour rectifying the same issue.