Hi there, just got back from OV2. Yes your phone will work. During the day you will automaticall connect to the local network, depending on what country you are in. Once you leave the port, the ship's own network kicks in (MCP) and your phone will connect to that. Not sure what the charges are, but there is a note in your cabin explaining these. There is a slight delay on the speech, but great for texting and making your friends jealous. Whilst they are watching Coronation Street, you are sailing across the Med heading for Cannes with dolphns jumping at the front of the boat!! - One thing to remember, put your phone on silent at night, otherwise yo will get a text "Welcom to France - etc etc" at around 7:00 each morning - Not recommended.
We were on OV1 last October and I recall there being a card in the cabin advising that you could use your mobile while at sea via the ships own network and it gave the network details for you to search for through your mobile. My own mobile picked it up automatically but you should be aware that the costs of using this facility are extremely high (sorry I haven't got any figures). You can of course use your mobile when close enough to land to pick up a signal from a land based transmitter at which point you are then subject to the overseas call costs of that particular service provider. Just make sure you are connected to the land based transmitter and not that of the ship. Hope this helps and have a nice cruise.