The PHA also say they will offer additional services, including support sessions for carers and relatives of those in distress or despair.
Complementary therapies will also be made available for those with the greatest levels of anxiety.
Investment will remain at the current level of £3.5m per year.
The PHA says that changing how the budget is spent will enable them to provide a "more effective service" to people in crisis.
The work of Lifeline is currently undertaken by Contact and is funded under the Suicide Prevention Strategy.
Contact's contract was due to end in 2015 but special arrangements were put in place by the Department of Health to extend it.
It is understood that the procurement process for the new service model will begin shortly.
The PHA has already held two 12-week consultations on Lifeline's future services.
The Public Health Agency (PHA) has confirmed the future of the Lifeline 24-hour suicide helpline service.