I had a similar problem recently. This is what happened and how I solved it.
Ordererd a new phone line, was told it would be free and that an engineer would be out in amximum of 2 weeks. 2 Weeks later, no sign, so I ring and get told it would be another few days. Rang again 1 week later to be told that it could take up to 28 days from that day. Registered an official complaint that same day and was told that somone would in contact within 2 working days. After 4 days I rang once a day, to be told that the customer care manager would call in the afternoon. After 7 days I rang twice a day and after 10 days I rang every hour. After 14 days the customer care manager sent an email saying that there might not be enough phonelines into the new estate. So it took them 5 weeks to tell me this. I went to the Eircom website and found their code of practice for complaints and also sent a query to ComReg. Both indicated that I could insist on the matter being looked into by the marketing executive. I rang Eircom again, to be toldd that they had never hear of such a request, so I read the code of practice out to them and after being on hold for 5 minutes was told that the escalation had been taken care of.
Sent an email to the customer care manager to tell them that I had asked for the case to be escalated and that I had contacted ComReg. 2 hours later I recieved a reply saying that someone would call out the following day. The following day a nice engineer came out, fixed the problem, activated the line and laughed when I told him that I had been told that maybe there weren't enough phone lines into the estate.
So, to get things done, escalate the matter according their code of practice and tell them that you contacted ComReg.