A common peice of advice for anybody travelling abroad for any length of time (e.g. doing a ski season) is to buy a local phone or SIM card. If you can get your phone unlocked, and for many phones you can do it free on various websites, then a new SIM card is the cheapest way but buying a new phone does let you check your messages on your existing number more easily.
The rationale is the high prices most phone operators charge for roaming calls and texts, and the assumption that calls with an operator from the country you are in will be vastly cheaper. However, this is not always the case as I recently discovered in France. Several friends told me that only one of the French networks provides decent reception in the Chamonix valley, so there seemed no point in shopping around for the best deal. I bought a basic thirty Euro SIM card, expecting to get nearly that much credit and in fact getting only five Euros included. I wasn't too happy about that, since every SIM card I have bought before in any country has nearly its full value included as credit, but I thought of how much money I would save by stopping using my UK phone. Until I found the (not well advertised) tarrifs and discovered that making calls in France cost 55 Eurocents a minute - significantly more than using my UK phone in a foreign country. Roaming charges have been capped by EU law for the last year or so, but it seems there is no limit to what a company can charge its customers while at home.
Anyway the moral is: research things before you rush in and buy, and compare the prices properly. There are several options for using a mobile abroad - buying a local SIM, buying a roaming SIM that works cheaply in many countries, or finding a phone operator in your home country that does good roaming tarrifs.