be easier to implement than a split. They also wanted to spare themselves and their customers the expense and burden of changing their numbers, which would have required a massive reprogramming of cell phones. The proposal for a split would have forced Vancouver Island's residents to change their numbers for a second time in a decade. The CRTC announced on June 7, 2007 that 778 would be expanded to become an overlay for the entire province starting that July 4. On that date, exchanges in 778 became available to Vancouver Island and interior residents, and a permissive dialling period began across British Columbia during which it was possible to make local calls with either seven or ten digits. Three CO prefixes in the 250 area code were reserved for use by Northwestel, as 13 of its 15 switches could not then handle multiple area codes, and its system could not accommodate ten-digit-dialling. The CRTC decided on an overlay after concluding that there was not enough time to implement a split before 250 was due to exhaust in January 2008. Effective June 23, 2008, ten-digit dialling became mandatory throughout the entire province, and attempts to make a seven-digit call triggered an intercept message with a reminder of the new rule. After September 12, 2008, seven-digit dialling no longer functioned. Overlays have become the preferred method of area code relief in Canada, as they are an easy workaround for the number allocation problem, as opposed to a split plan. On June 1, 2013, area code 236 was implemented as a distributed overlay of area codes 250, 604, and 778 and was expected to be exhausted by May 2020. As a result, area code 672 was implemented on May 4, 2019, as an additional distributed overlay to relieve area codes 250, 604, 778, and 236. Service area and central office codes 100 Mile House: 395 456 593 396 706 Armstrong: 546 Beaverdell: 484 Bella Bella: 957 Bridge River Valley, including Bralorne, Brexton, Gold Bridge, and Gun Lake: 238 Campbell River: 201 202 203 204 205 286 287 346 504 830 850 895 923 Castlegar: 304 365 608 687 Chetwynd: 788 Christina Lake: 447 Cranbrook: 417 420 421 426 450 464 489 581 919 Creston: 254 402 428 431 435 977 Comox: 339 890 941 Courtenay: 207 218 331 334 338 465 585 650 702 703 792 871 897 898 The Cowichan Valley comprises