Your iPad is set to Automatically select your Network Operator, so if your 8ta/Telkom Mobile signal is weak, it will switch to MTN, cos you can roam for free (voice) on MTN.
If you want to have peace of mind and not roam on MTN network - ask data desk nicely to provision your sim card to make use of TELKOM MOBILE network only... That why you don't get any hidden surprised
Great stuff Telkom Mobile.
Monitoring the forums and assisting users with their problems.
Guess I made a good choice when I subscribed to your services.