FNB - bad service

I called FNB and spoke to Siya who told me to hold the line and I waited 20 minutes without any feedback. Under normal circumstances, I receive immediate help and get assisted in less than 5min. I guess some people take advantage of working remotely. I made a second call and spoke to Mabunda who hung up the call when I asked about the process to follow for a complaint. Disappointed by the service received.