no inernet when power is down

Horrible , horrible , horrible customer service , rain is quick to debit but cannot assist with a query i have been having continuous connectivity issues, especially during load shedding, we bought an inverter for the reason to have internet when the power goes out. We work from home, and it was working fine until Rain Recommended to upgrade to a 5g sim wich will now work in my area since i have the 5g sim inserted i have no inernet when power goes down. What seems to be the issue??? im livving in paarl right next o where they say they have an Tower