I'm looking for suggestions on what the costs are (and which provider) for a 1month period of useage. This would be for a smartphone, ideally to have unlimited calls/messaging/Data.

We have 3 phones which we'd like to set up, but in the least 1 would be the requirement.

Whether the sim can be picked up at the airport, or ordered ahead of time from say Ebay?

Appreciate the help,