Rain (5G) What must we do?

We've been with Rain for almost 2years (on a 4G plan) they upgraded us to a 5G with router and all (23 Aug 2024), we had to phone them the day of receiving the upgrade due to all our devices not picking up the 5G router.. On Sunday (1 Sep 2024) there was a power dip where we live, power went of and came back again. After the power dip the router does not want to switch on so we phoned Rain (4times) to ask if we are doing something wrong because the router not powering on. Rain then informed us that due to the router being in our possession we broke it and have to pay R4000 all because we did not plug out our device; they also logged the power dip (did not last more than 3sec) as Load shedding - There was/is no schedules for any power dips in our town... what must we do?? We do not think we are liable for the R4000. After telling them we are not going to pay the R4000 and they must cancel our subscription they hang up the phone. If we do comply with plugging out our devices just incase of power dips/ power outages / unplanned cable fault we will never be able to plug our devices back in.