Cellular base stations use time-frequency Resource Blocks (RBs) on shared radio bands. Tower congestion occurs strictly when simultaneous user bandwidth demands exceed the tower's instantaneous megabits-per-second (Mbps) capacity. Latency spikes and queues form regardless of how much total volume users have in their accounts.
Data balances (MB/GB) are purely numerical entries in a database ledger. Stored data volume consumes zero radio spectrum, zero tower power, and zero channel capacity when idle. Mobile data expiry rules are business billing structures rather than physical cellular radio constraints.