Manx Telecom's been hit with a £100,000 fine over providing an interconnector between Sure and BT.
The company was investigated by the Island's telecoms regulator over the negotiations after Sure accused it of withdrawing the cheapest and efficient options.
The Communications and Utilities Regulatory Authority found MT hadn't negotiated in good faith within a reasonable time.
CURA said the company should produce a policy showing how it would avoid breaching its licence in future - and pay a £100,000 penalty.