Incorrect capturing of ID biometrics

I went to FNB Merchant Place this morning for an appointment to capture my biometrics for a new ID document, as I have recently gotten married. I was told by those assisting me that as I am married under a Civil Union I could not change my surname as this is purely for same-*** marriages. I was thus turned away and told to contact home affairs. The law states that hetero***ual couples can be married under this act. I spoke to my marriage officiant post the appointment. The officiant indicated this issue has never come up before and the bank is at fault. I cannot reach FNB Merchant to discuss the matter as there is no helpline for this service. My only option now is to go to Home Affairs and start the process all over again. I am deeply disappointed with FNB Merchant Place's service and require assistance on the matter urgently.