Comcast has expanded the list of cities where it imposes data caps, with customers in parts of Arkansas, Louisiana, Tennessee, and Virginia facing new data limits and overage charges.

DSLReports reported the expansion yesterday and reprinted an e-mail that is informing customers that they will face the data caps beginning December 1.

"While we believe that 300GB is more than enough to meet your Internet usage needs, if for any reason you exceed the 300GB included in your plan in a month, we will automatically add blocks of 50GB to your account for an additional fee of $10 each," Comcast wrote. "We’re also implementing a three-month courtesy program. That means you will not be billed for the first three times you exceed the 300 GB included in the monthly data plan."

Customers can pay an additional $35 a month for unlimited data, the e-mail said. In other areas, Comcast has charged $30 a month extra for unlimited data.

Newly capped areas include Little Rock, Arkansas; Houma, LaPlace, and Shreveport, Louisiana; Chattanooga, Greeneville, Johnson City, and Gray, Tennessee; and Galax, Virginia.

Cities and towns in Comcast's "Data Usage Plan Trials" already included Huntsville, Mobile, and Tuscaloosa, Alabama; Tucson, Arizona; Fort Lauderdale, the Keys, and Miami, Florida; Atlanta, Augusta, and Savannah, Georgia; Central Kentucky; Maine; Jackson and Tupelo, Mississippi; Knoxville, Memphis, and Nashville, Tennessee; and Charleston, South Carolina.

A few zip codes in Texas near the Louisiana border are also affected, as are some in Illinois and Indiana near the states' borders with Kentucky.

Comcast has steadily introduced caps into new areas, testing customers' responses before a potential nationwide rollout.

Even before the expansion, customers were complaining about Comcast's data caps to the Federal Communications Commission. The FCC hasn't outlawed data caps, but in its net neutrality order the commission laid out required procedures for disclosing caps to customers and said it would review whether specific caps violate its "no-unreasonable interference/disadvantage" standard on a case-by-case basis. Under that standard, caps would violate the FCC's rules if they "unreasonably interfere" with the ability of consumers and online service providers to reach one another via broadband.

Consumer advocacy group Free Press yesterday called on the FCC to investigate Comcast's caps, saying that "Comcast continues to exert its dominance in the uncompetitive market for high-speed Internet access," and that the caps are "part of Comcast's scheme to stifle innovation and choice in online video and cloud-based services."

Comcast, the nation's largest cable and broadband provider, has been willing to impose data limits in areas where it does face robust competition. While it has so far avoided the Northeast where Verizon FiOS is prevalent, Comcast is imposing a cap in Chattanooga even though the community-run Electric Power Board offers uncapped gigabit fiber service for $70 a month.

Comcast recently launched its $300-a-month 2Gbps fiber service in Chattanooga. EPB then launched 10Gbps service, also for $300 a month. (Unlike Comcast cable Internet, Comcast's fiber plan doesn't have data caps.)

Comcast, which has poor customer satisfaction ratings, insists that data caps add some "fairness" into the system. "About 8 percent of all Comcast customers go over 300GB," according to an Associated Press story last week. (The figure was 2 percent in late 2013.) "Data caps really amount to a mechanism 'that would introduce some more fairness into this,' says Comcast spokesman Charlie Douglas."

That statement is similar to what Comcast has previously told Ars. But in one case, Comcast's vice president of Internet services acknowledged that setting the monthly data limit at 300GB is a "business policy," not a decision driven by technical necessity.

UPDATE: DSLReports points to a Comcast support script apparently leaked by employees. The script tells employees not to use the phrase "data cap" to refer to what Comcast calls its "data usage plans." It also instructs employees not to tell customers the program is about congestion management. Instead, they should tell customers that the "data usage plans" are about "fairness and providing a more flexible policy to our customers."