How can I set English (South Africa) the only language option

Look for the language or interface language option within the program's Settings or Preferences menu.

HI goonRain​ 

Kindly, try to perform the steps below and let me know if it works for you. 

1.Press Win + I to open Settings

Go to Time & Language > Language & region

Under Preferred languages, click Add a language

Search for English (South Africa) and click Install

2. Set as Default Input Language
After installation, under Preferred languages, drag English (South Africa) to the top of the list

Or click the three dots next to it and choose Move up

It will now be the default display and input language.

3. Remove Other Keyboards
Still under Language & region, click on any other installed language (like English US, UK, etc.)

Click Remove

If "Remove" is grayed out, it means the system still needs it. First set South Africa as default, then restart your PC and try again.

4. Check Keyboard Layout
Under Preferred languages, click on English (South Africa) > Language options

Under Keyboards, make sure English (South Africa) is there