Australia, regional in Queensland state.

I've noted similar in the three main networks, where I've suspected the load balancing algorithm for traffic adjusts a setting in regard to cut off on signal strength hasn't been quite set right. Obviously at times dealing with extraordinary use at the time, one expects balancing. One network in my locale a few years ago, it was quite clear it was either over subscribed, techs made a mistake adjusting the algorithms ... or just too many people trying to use that particular one tower, and three people in the same spot could often note the three different states the network could be in, none, unavailable, signal - this existed for many months. The balancing has been tuned up a few times since then. I have found when the network's coverage was spotty for voice calls, one could generally use data to get online albeit as slow rates.

Recently the main network I'm using (Optus,) I've noted missed calls that went to voice mail, I have not heard the call at all. I have been blaming signal though I don't have it on me (sits outside the window up high) to ensure the phone has good signal. However on data over wifi, the network often drops out for a minute or more at times.