NEW Credit Card terminals defective

So Nedbank came and upgraded my credit card terminals in my store yesterday as the older ones started giving issues, the problem I have is how can they put in new terminals that have NOT been tested!!!!! I cannot redeem "Gift Cards" I work in a toy shop where we redeem lots of Gift cards, I now have to turn away customers that would like to redeem their cards until Nedbank decides to fix the issue! Very unprofessional!