Poor customer service and no explanation for disconnection

Today I woke not able to use my sim card.It was showing emergency calls only.I called the call centre and was advised that they are resetting my connection.I will then need to switch off my phone and switch it back on.The problem persisted still and I went to the nearest store in Westgate.I was advised that someone did a sim swap on my number.I asked when and how someone did a sim swap because my phone was working until the morning.No answer was provided and they did something on the system.After a few minutes I was told my connection has been resolved.I asked how do I prevent this from happening again and can they not see on the system where sim swap was done.Still no answers provided. Such inconvenience of not being able to use my phone and people not able to get hold of me.