Industrial action threatened by Eircell and Eircom workers will leave the 087 network without technicians to fix coverage blackouts.
The action could then affect Eircom’s fixed line business.
Unions representing 12,000 staff in Eircom and Eircell have served notice of industrial action.
Four unions have notified Eircom Chief Executive Alfie Kane that they will strike next Wednesday.
About 100 staff at the company downed tools for five hours last Friday, and it is feared some call centre operations in College Green, Dublin and Dundalk,
could take unofficial action before next Wednesday.
The dispute centres on compensation for 1,200 Eircell employees who will transfer to Vodafone as a result of the sale of Eircom’s mobile wing to the British group.