Great service - but reversal of incorrect ratings should be made possible

I was served by Busi Matsaug at FNB recently and I must commend her on the excellent level of service she conveyed to me. She was patient, she took the time to explain everything to me, and she ensured that I made the best banking decisions for my situation. I erroneously selected the wrong number when I got the SMS from FNB to review the service I had received, and I was unfortunately told that I cannot reverse this. There should be a way to reverse this as it is easy to make mistakes.