Vodafone claims new price controls by ComReg may affect its annual revenues by up to €4m a year.
The telecoms provider has brought an urgent Commercial Court action against the regulator's changes to mobile phone termination rates.
These are charges imposed by operators to facilitate incoming calls from a different network provider.
Vodafone said that its termination rate has dropped from an average of over 9c to more than 3c between 2007 and 2012.
The court has been told that in Revenue terms, that's a drop from more than €95m to €31.8m.