Treated as a ********

Yesterday afternoon I was in urgent need of cash. Stopped at Glen Acres shopping centre to withdraw money from Standard Bank OTM but found that due to an extension of Nedbank the OTM's have been removed. As I was in a hurry I decided to withdraw money from Nedbank's OTM using my American Express Credit Card. After typing in all the necessary information a message popped up to say that the transaction was not completed and that my card is retained and that I should visit the branch. This I did and it probably took me 30 minutes (keep in mind I used this facility because I was in a hurry) to retrieve my card. No explanation could be provided as to why this happened. I am now too afraid to use the card because of the embarrassment it may cause if, for instance, the card is declined in the presence of one of my clients. What is the solution to this - close the account???