I'm unsure what motivation any operator would have for intentionally degrading service, but there's a lot to be said for perception. Some users get concerned when their indicated service is reduced, when this can often mean higher-band carriers are in use and thus improved service should result.
You mention that your daughter's phone was unable to make a call to you yesterday - was she unable to dial out? And if so, did her phone show coverage indicators? Was she able to send a text message? Or was it that her outbound attempts worked, but your phone was unable to receive? In which case the same questions apply to your phone - was coverage displayed at the time?
If calls are failing when coverage is shown, then that's a problem which should be reported. A methodical approach is often best with fault finding, to identify the cause of the issue.
