The Federal Trade Commission and six states are suing Frontier Communications for not delivering the internet speeds it promised customers and charging them for better, more expensive service than they actually got.

In its complaint, filed Wednesday in federal court in California, the FTC said thousands of Frontier customers have complained that the company was not delivering promised speeds. Customers said they couldn’t use the internet service for the online activities they should have been able to.

The complaint concerns what’s called DSL internet, an older type of network that’s sent over copper telephone wires. Phone and cable companies today build networks which can handle much faster speeds. The FTC says Frontier provides DSL service to 1.3 million customers in 25 states, mostly in rural areas. It has about 3 million internet customers overall.

Involved in the suit are attorneys general from Arizona, Indiana, Michigan, North Carolina, Wisconsin and the district attorneys’ offices of Los Angeles County and Riverside County on behalf of California. The complaint was filed in the U.S. District Court for the Central District of California.