How long were the connections not working? If it was just a few minutes, it could have been a momentary glitch either on the phone or in your carrier's network. If it was longer, it's possible there was an actual service outage in your area. Shortly after I bought my first Android phone, a couple of years ago, Verizon went through a period of several weeks when there were regional outages all the time. I was really starting to question my decision, but they did eventually get it fixed. OTOH, if the problem was in the phone, it could (I think--someone else here will know better) be a SIM card issue. If it happens again, you might want to check to be sure the SIM is properly seated.