SIM swapping/exchange is usually phase two of a fraud attack. Initially, they send a phishing email (or other similar phishing attempt) to get all your banking details. These details can also be stolen using Trojans/Malware. They also work towards getting the victims personal information and may even go as far as stealing identity and creating fraudulent ID documents. In order to use all of this gathered information, they need access to the victims mobile messages - hence the SIM swap
Safety Tips:
Be vigilant and try to stay aware of your cellphone's network connectivity status. If you realise that you are not receiving any calls or SMS notifications for a long time, something may be wrong and you should make enquiries with your mobile operator to be sure that you have not fallen victim to this scam
Some Mobile network operators send customers an SMS to alert you of a SIM swap - which means you can act and stop this fraud in its tracks by contacting your mobile operator immediately
Do not switch off your cellphone in the event you are receiving numerous annoying calls, rather don't answer the calls. This could be a ploy to get you to turn off your phone or put it on silent to prevent you from noticing that your connectivity has been tampered with
Register for Alerts (SMS and Email) so that when there is any activity on your bank account you will receive an alert
Always check your bank statements and online banking transaction history regularly to help identify any issues or irregularities