Sim card issues

<p>i went for a sim swop to use my mtn sim on a different phone. This was due to physical sim card size and the slot. The sim card does not work on the phone, but testing o.k on 3 other phones and then another not working. I went back to the mtn store as it is a sim issue, not phone issue. All i asked was to use a different sim. I was kust told the phone is network locked then told the phone is broken then told software is outdated. Every single other sim that was tested on the phone, works 100%. It is the sim. Please asssit me in getting sorted as i do not want to go back to the same mtn store. 3 different people, 3 different theories. It is the SIM! I went to the vodacom store right next door and their sims worked perplfectly. They said my device is working fine. Please asssit me here to get me a working sim card, alternatively i will port my number to a different network- like i have done with previous contracts</p>