Sim swop issues

I had a cell c contract for many years through Autopage. Before they closed down I changed over to a pre-paid option. For 2 years I have been on this option using the same phone that I got on my last contract. Yesterday I bought a new contract for my son and had to do a sim swop. No issues no hassles (this was with MTN). So I got myself a new phone too and I have to get a new sim a s the bigger one does not fit. I went to cell c to do this. Firstly I was told my number is not registered on my name but on a dummy company which was most likely created by Autopage when I changed from contract to pre-paid so they cannot change my sim card. Then a call centre agent tells me I have to go buy another sim at Pick & Pay and then do Rica and then only can I do a sim swop. I am extremely confused and highly frustrated. All I want is to be able to use my new phone and nobody is able to help me.