The point of the DNS change was to see if you get sent (for akamai sites) an Akamai cluster besides the one Vox hosts in Durban, because there may be a problem at Vox in Durban.
Testing Vox with the DNS change doesn't help for that aspect ...
You may want to compare e.g.
https://www.emirates.com . That is one we used today troubleshooting with a customer. With SAIX Durban DNS they get 104.94.82.217 which works for HTTP (well, small HTTP such as the redirect to HTTPS) but not HTTPS (or not with larger packets)
If I query that on 105.225.0.1 I get 2.21.234.224 which is on our network, but I can't see if it works for HTTPS over LTE.