You could always try routing it through a VPN... that should also work in theory
Vodacom: 41.1.162.233 (epdg.epc.mnc001.mcc655.pub.3gppnetwork.org)
Cell-C: 41.50.128.53 (epdg.epc.mnc007.mcc655.pub.3gppnetwork.org)
Mtn: 41.208.50.116 and
41.208.50.117 (epdg.epc.mnc010.mcc655.pub.3gppnetwork.org)
Telkom: 41.246.191.254 (epdg.epc.mnc002.mcc655.pub.3gppnetwork.org)
Ports: 4500 & 500 (udp), 143 (tcp)
You could implement the VPN at router level, or even simply install the vpn app on your phone. Cloudfare warp is a good (and free!) one that should work - and if you use something like Warp, you won't need to worry about configuring any of these IP's/ports, just enable the VPN and everything should start working on its own...
Sources:
https://www.netify.ai/resources/applications/3gpp-network
Recently had to scrape this info together. Hope it can help someone else in future. epdg.epc.mnc001.mcc655.pub.3gppnetwork.org - Vodacom epdg.epc.mnc002.mcc655.pub.3gppnetwork.org - Telkom epdg.epc.mnc007.mcc655.pub.3gppnetwork.org - Cell-C epdg.epc.mnc010.mcc655.pub.3gppnetwork.org - MTN
mybroadband.co.za