So anyway, I checked online and it said that I was eligible for an upgrade, so I did. With that is a 2 year service plan. Is that an extension on the existing plan?

Also, when you upgrade phones, does your number change if you're keeping the exact same plan, just changing the phone?

I have no idea. :\

Oh and do you keep your old SIM card or chip or whatever that thing is?
Or do they send you a new one with the phone?