I've never had a cellphone before.I just got my Nexus 5. I ordered it online and I asked for a new phone number. I put the SIM card in and set up the phone, but I can't get any service, even right next to the nearest cell tower. Also, my phone number says it's "unknown" and there is nothing else telling me what it is. I don't know if I have to activate it, but in the Self Serve it says you need your number to do so...help?