Trade-in credits are not showing up on our bill

Recently upgraded 2 lines this past Nov. 2020 because of a Promo.

Upgraded a 6s Plus to the new 12 (128 GB) and an 8 Plus to the new 12 (128 GB).

Upon purchase of trade-in online, the 6s Plus to the 12 was quoted at $16.67/month for 30mo.

The 8 Plus to the 12 was quoted at $1.67/month for 30mo.

We received our new phones, the 8's replacement came with a return box and the was shipped out the following day (I still have the tracking number and photo).

The 6s Plus's replacement did not come with a return box with the 12 and had to wait for a separate return label. It was sent out a week late.

These phones were maintained well and kept in cases and glass screen protectors. Overall, should be worth more than just $0.

We just received the bill and for both lines showing an installment payment of $28.34. I feel this is incorrect and the online method very misleading. If I will be paying for the full price of the phone, I never would've traded in the phones in the first place.

Tried to call AT&T but all lines are busy. I need clarification.