Verizon $699 trade-in value iPhone 4 or newer *new line not required* (YMMV)
For EXISTING CUSTOMERS Verizon has a "loyalty trade-in promotion" where with any iPhone 4 or newer they'll give you $699. I just completed this with replacing an iPhone 7 and iPhone 8 with 12 pro's. The deal comes in as a credit spread out over whatever term you choose for the new phone, $29cr for 24mo in my case.
I have been hunting for a deal on the new iPhones for a couple of months. Was going to do the Walmart $200 off promo, and then found myself calling Verizon Sales for help on the Disney bundle. I politely questioned how this is possible and verified 10 times that I'm keeping my number, and no "new line" funny business. He advised that Verizon Telesales (not customer service) have different/more authority and promotions than available online or in store.
I was still skeptical but searching the internet I found Reddit posts with users having the same experience. And sure enough, now I have my $45 charge (12 pro 256gb) and $29 trade in credit on my bill.