SimSwop from MicroSim to NanoSIM

I just had the most absurd experience at CellC Cape Gate branch. I have a microSim that I use for Whatsapp. But now I bought a new phone that only takes a nanoSim. I tried to do a SimSwop.

Firstly I phoned the Call Centre. But they needed the last 5 numbers I dialed. But because I use the number just for Whatsapp I don't have the last dialed numbers. So the Call Centre sent me to the store carrying my ID, proof of address and my microSim.

At the branch, they couldn't help me even though I had my ID, The MicroSIm and proof of address. And I was sitting in front of the consultant. The manager is out of the store till March 15th. They couldn't help me. How is this possible?