I had similar frustrations with Eircom and another small operator, which annoyed me completely.
I actually got rid of the DSL phone line, and got my broadband thru NTL cable (may not be available in your area). For my landline, I set myself up with Blueface.ie - I paid about 80 for the modem, and able to use normal phone. Got a normal number, free local and national calls for 6 months, and to be honest v cheap after that. Not sure what current tarrifs they are charging as I am on a business account now with them. I'm sure there are other providers in the same space. Its great because you can manage your account on line, divert phone line as and when required, get emailed your voicemail...
Have to say I felt great when calling eircom to disconnect the traditional DSL phone line service!