Am I able to use call13434 if NTL or another company than Eircom is my service provider?

Yes! Once you have registered your telephone number and payment details you can start using Call13434 immediately. From non-Eircom landlines just dial 01 6850850, wait for the voiceprompt and enter the follow-on telephone number. For example: 01 6850850 -wait for voiceprompt- 001 818 456 4567.
Or from mobiles* dial 01 6850850, wait for the voiceprompt and enter the follow-on telephone number. After dialling the follow-on telephone number do NOT press the green ?send? button on your mobile again otherwise the call may be carried by your mobile operator!
01 6 (Dublin area) calls may come out your inclusive free minutes or your operator may charge separately for calls to 01 6 numbers depending on your operator and tariff plan; please check with your mobile operator for correct rates.