number exhaust
n. The state or condition of the telephone system having no available telephone numbers.
Other Forms
Someday soon North American telephone numbers might add up to 12 digits, including area code, instead of the current 10.

Verizon, Qwest and BellSouth have urged the Industry Numbering Commission, which regulates the distribution of telephone numbers in North America, to "be proactive" about what the phone companies see as the newest threat to the dwindling supply of available phone numbers: voiceover Internet protocol, or VoIP. …

The phone companies insist that VoIP has the potential to eat up 10-digit numbers faster than cell phones, fax machines and pagers did. This would hasten the day North America runs out of unique phone numbers, requiring an entirely new numbering scheme. …

A few years ago, number exhaust was projected to happen in 2009. With the collapse of the telecom boom, however, that date was pushed to 2031. Approximately 1.3 billion telephone numbers currently remain available.

"The old patterns of number exhaust were pretty well understood, but they may not make sense in this new VoIP world," Sanders said.
—Patrick Di Justo, “Out of Phone Numbers? Add Digits,” Wired News, February 18, 2003
1991 (earliest)
PacTel said Bellcore assigns codes "on an equitable basis" and "all players are treated fairly." Other commenters, whether or not they supported inquiry, expressed caution over whatever new scheme might emerge. PacTel also said "number exhaust" — running out of combinations of codes — means RHCs would have to spend millions to reconfigure switches and upgrade software, and would support FCC inquiry into cost recovery.
—“PacTel: FCC can offer only partial solutions to numbering,” Communications Daily, December 30, 1991