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The gas company needs to contact the CA and tell them to cease collection efforts and return the account to them.
I've had similar situations with both AT&T and Sprint. A CA was reporting, but the vendor legally owned the debt. In both cases I paid the vendor (AT&T/Sprint) directly, sent a copy of the $0 balance receipt to the CRA's, and they immediately deleted.
When you pay the OC directly, the CA cannot stay on the report because they no longer have your account.