Area code 604 had served as British Columbia's sole area code for 53 years before 250 was created as the area code for Vancouver Island and the Interior in 1997, with 604 cut back to serve Vancouver and the Lower Mainland. This was intended as a long-term solution; however, within four years, 604 was on the brink of exhaustion once again due to Canada's number allocation system. Every competitive local exchange carrier is allocated blocks of 10,000 numbers—corresponding to a single prefix—for every rate centre where they plan to offer service, even in the smallest hamlets. While most rate centres do not need nearly that many numbers, a number cannot be allocated elsewhere once assigned to a rate centre and carrier. This results in thousands of wasted numbers. While numbers tended to be used up fairly quickly in the immediate Vancouver area due to its rapid growth, the number allocation problem was particularly severe in the Lower Mainland. It is home to most of the province's landlines and cell phones. To solve this problem, area code 778 was created on November 3, 2001, as a concentrated overlay for the two largest regional districts in the Lower Mainland, Metro Vancouver and the Fraser Valley Regional District. The rest of the Lower Mainland continued to use only 604. Nonetheless, the implementation of 778 made 10-digit dialing mandatory across the Lower Mainland. In early 2007, the Canadian Radio-television and Telecommunications Commission faced the prospect that 250 would exhaust in early 2008. Relief proposals included:
a geographic split that would have seen the Interior retain 250, with Vancouver Island switching to a new area code
concentrated overlays covering part of the 250 territory
Ultimately, the CRTC concluded that there was not enough time to implement a split before 250 was due to exhaust. Additionally, the major landline and cell phone providers in the 250 territory contended that an overlay would be far easier to implement than a split. Telus and other carriers wanted to spare their Vancouver Island customers the expense and burden of changing their numbers for the second time in a decade. Accordingly, the CRTC announced on June 7, 2007, that 778 would become an overlay for the entire province effective July 4, 2007. Overlays have become the preferred method of relief in Canada, as they are an easy workaround for the number allocation problem; no area codes have been split in the country since 1999. As of June 23, 2008, ten-digit dialling became mandatory across British Columbia; attempting to use seven digits would trigger an intercept message reminding callers of the new rule. After September 12, 2008, seven-digit dialling ceased to function. This was intended as a long-term solution, but within four years 604, 250 and 778 were close to exhaustion once again. To solve the problem, area code 236 went into effect as an additional overlay for the province on June 1, 2013. Area codes 604, 250, 778 and 236 are expected to be exhausted by May 2020. As such, the CRTC has ordered the introduction of a third overlay for the province, 672, which was put into effect on May 4, 2019.
