The Court of Appeal has turned down an appeal against a High Court ruling which found Telecom did not abuse its dominant position in the residential market when it introduced a new service in 1999.
The Commerce Commission lodged the appeal, and says it's disappointed with the decision and is studying the ruling.
In 1999, Telecom said residential customers would be charged for calls to internet service providers unless they used an 0867 dial-code.
Telecom made the 0867 number range available to other telecommunications network operators only if they agreed to terms that meant Telecom was not required to pay charges relating to those calls.
The commission claimed that in introducing the 0867 scheme Telecom sought to prevent or deter competitive conduct by other carriers and ISPs.