I'm going on a cruise this summer and I'm bringing my phone. I don't need to able able to recieve/make any calls or texts, and I don't need to use wifi or internet. I just wanna bring it along because it has all of my music on it, and since I have an iPhone 4s, I don't have an ipod. Can I just put it on airplane mode to avoid roaming charges? Or should I take the sim card out for the week that I'm gone?