Unchange booking requests

I contacted the agency on Tuesday to make changes to an existing booking, flight leaving for Jhb to Durbs Thursday the 21st. I asked that the changes be moved to the 5th of August. Average waiting was stated to be 50min on the call so I then opted to make changes on the app. A query was open and responded to the very evening but with incorrect changes. I immediately responded with a request for correction and requoting. The email was not responded to, I then created another query on the 20th but that was still not responded to until I got an email late on the 21st stating a now show for my plane..I can't lose my money when I made requests that were not actioned. Kindly assist me in this regard please. Travel ***, from Jhb to Durbs.