Greenbacks Rewards - Amex card

Good day I have been trying to get hold of the Nedbank Rewards department since middle October on their tel nr, and also sent an e-mail, but no success. I have even now tried to work through the Client Care Centre, but the agent could not assist me and transferred me to another person/department where the phone just kept on ringing, then it automatically was diverted back to Client Care and I had to wait again for another agent to assist. After holding on for quite a while I put the phone down. Please contact me regarding my greenbacks voucher which I qualified for, but never received the voucher.