(CBS) — Tens of thousands of northwest suburban residents who have been part of a program to shop around for the best electric rates were left confused after receiving letters telling them they were being switched back to ComEd.

WBBM Newsradio’s Mike Krauser reports those who got the letters are members of the Northwest Electric Aggregation Consortium; and live in Arlington Heights, Buffalo Grove, Lincolnshire, Long Grove, Palatine, Wheeling and Vernon Hills.

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Those residents pool together to negotiate lower electric rates with ComEd competitors.

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ComEd recently sent them letters informing them they were being moved from their current electric supplier, Integrys, back to ComEd, and would be locked into rates. The letters were sent in error, triggered by a new electric deal with a third supplier, Constellation.

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The residents were being told they would not be switched back to ComEd, and don’t need to do anything about the letters.