All 4 mobile companies have similar plans for the iPhone if you sign up for a 2 year contract. Essentially you purchase the phone up front for around $22 000 NT, but each month your phone bill is deducted from that balance, so you won’t need to pay any bills for the first year or so. Unlimited data plans are around $800 NT so with a voice plan you’re looking around $1350 NT per month.
You can find more details about how this works here: Getting a Phone on Contract (How to Read & Interpret Rate Tables)