If you don’t like your carrier changing both at once is the best thing to do.
I new carrier will throw in all kinds of shit for a new customer are you kidding ?
Just go to potential new carrier and tell them you thinking about switching if you give me a free iPhone .
You would never get that changing one at a time .
chop is 100% right on this.
I was a long time AT&T customer and switched to Verizon. Was able to get 3 phones for the price of 1 plus other crap