Comcast Corp. is shutting down one of its two telephone services in Greater Hartford and this week disconnected any customers who had not yet switched to a new service plan.

The company is discontinuing Comcast Digital Phone, an older service that was offered to former customers of AT&T; Broadband.

The shutdown does not affect Comcast Digital Voice, the service used by most of the company’s phone customers.

Comcast declined to say how many customers were disconnected and left without service. The company said it has been helping customers find other phone service, including its own Digital Voice service.

The disconnections, which took effect Monday, still allow customers to call 911 and Comcast customer service.

The company sent letters, called and in some cases went door-to-door to inform customers of the service termination and possible loss of their phone numbers.

“Comcast has made numerous contacts to all existing Comcast Digital Phone customers in the Hartford market well in advance to alert them to the pending discontinuance and, ideally, help move them to a new phone service to avoid any interruptions in service,” said Kristen Roberts, a spokeswoman for the company.

Nevertheless, some customers found themselves without phone service Tuesday. Peter Adomeit, a West Hartford resident, said he has been working with AT&T; to replace the Comcast phone service. The installation, however, isn’t complete, leaving him with limited phone service.

Attorney General Richard Blumenthal said his office received several calls from Comcast customers on the disconnections. He said his office is currently looking into them and has requested information on the number of people who lost phone service.

Comcast eliminated the older phone service because it operated on an outside network. Comcast wants to concentrate on one phone service that uses the company’s own network, Roberts said.

Contact Mark Peters at mrpeters@courant.com.