Hello, received a new phone today. Sales person didn't activate my new SIM card so I'm trying to do this myself online. When it asked for the old and new SIM card numbers, it keeps prompting me that my old SIM card is invalide.
Welcome to the community!
If you order the new SIM card online or through customer support it would not be activated as it will deactivate your old SIM card and would not be able to use your service until the new one comes.