Signing up for installment is required, yes. You can just pay off the remaining $200 via AT&T, though. There's no monthly bill credits to lose so you're not really locked in."Requires 30 months, 0% APR installment agreement,"
Seems like a bad deal at Walmart
The $200 off is a cash discount and the loan agreement will show a financed amount of $200 (for 64GB model).