If ur buying a prepay sim then Meteor have €0.99 a day max, which gives you 50MB, this would be for phone, not for dongle. Vodafone also have something similar, but I think it has to go through their portal. I'm a Meteor customer, but use wifi mostly. If u decide for Meteor, you will have invest some energy in getting the Customer Care Helpline to turn-on full ISP access for you, otherwise you'll end up on their portal. Oh at present O2 are giving out USB dongle for free 3 day trial, but u will need proof of an Irish address I think, utility bill +deposit.
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