In 1999, when I moved from Boston to New York in order to transfer to a different university, there were a lot of logistical hassles along the way. I remember that one of the worst was changing my mobile phone.
Back then in the US, our mobile phone plans still had 'home ranges' outside of which you would pay a roaming surcharge to use your phone. This range was usually your state, or maybe a zone of three states. My mobile phone with a Massachusetts number would have been roaming in New York. So I had to change my phone plan. I also had to change my Massachusetts phone number to a New York one so that when people called me in New York they wouldn't be charged for a long-distance call.