Not a new problem.
"So If you're doing spectrum policy, it really helps to consult the physicists, so you make rules that are consistent with the constraints of Maxwell's wave equations. If you're doing broadband policy, it really helps to consult the stochasticians, so you make rules that are consistent with the constraints of packet-based statistical multiplexing," added Geddes.
Stochastic models used to decide how many voice calls at once an exchange can support, no exchange could ever support all users at once. The "engaged" tone might mean connection capacity is used up on the local exchange.
Most of what is advocated regarding Net Neutrality is bonkers. Especially so on a Mobile connection.