Starting Monday, cell phone portability goes nationwide. That means cellular customers can keep the same phone numbers when switching to new wireless carriers.
It also lets them transfer the number from a traditional landline phone to a cell phone in the same area.
The portability rules went into effect last November in the 100 cities with the most people, and now it's expanding to the rest of the country.
That means millions of people in small cities and rural areas will be able to take advantage of the rules. But the Federal Communications Commission estimates they make up only about 30-percent of the population.
The rules already covered the other 70-percent when they took effect in November.