Hi! I'm going to USA for two months and I will need a SIM mainly for incoming calls, but messages is definitely what I'm going to use the most. I'm not looking for data usage or things like this, so I was wondering which is the best and cheapest option to get a prepaid nano sim card just for using it for that period of time. I already have an unlocked iPhone 5, so the only thing I need is the SIM. Thanks!