SIM card not activating.

Hi, I have brought an iPhone 6 from the US to South Africa. It was on verizon and has been carrier unlocked(I have double checked with them). The sim card won't activate it gives the following message: "The SIM card that you currently have installed in this iPhone is from a carrier that is not supported under the activation policy that is currently assigned by the activation server. This is not a hardware issue with the iPhone. Please insert another SIM card from a supported carrier or request that this iPhone be unlocked by your carrier. Please contact Apple for more information."

I have taken a working Sim Card from an MTN number, and a working Sim Card from a Vodacom number both with the same result. What is it that I still need to do?