Does British Airways have staff at the office?

Booked a flight and car through BA Executive Club, tried to change a domestic flight time for the past 4 days. No-one answers the phone. Holding on for one and a half hours at a time. Drove to Cape Town International Airport, but BA could not change anything on their system, because I had a rental car through Avis. Same telephone number was given to me for BA Holidays and a cell number. No-one answers that cell number. Sent whats apps, gets read, but no response. Frustrated and simply don't know what to do anymore. My flight out is in 4 days, and it needs to be changed.