Can't get new phone unlocked for daughter's study-abroad trip.

My daughter leaves Feb 1 for 6 months in New Zealand.   While there she will need to get a SIM for the local carrier in order to communicate with others in the program while there.   The issue is I cannot get her new iPhone 15 unlocked.

Back in October Xfinity had a great trade-in offer for her paid-off iPhone 11 to buy a 15 with 24 monthly payments.  Unbeknownst to us the phone is locked to Xfinity Wireless and they will NOT unlock it under any circumstance until the phone is paid off in full.  I understand the reasoning behind it but if that phone is on my account and I get a bill for it each month and I pay that bill each month then why would the phone not be able to become unlocked.  If I do not make a payment on my account then I'll be past due and Xfinity can easily turn off all my service and send me to collections.  Which of course, I would never do.   

So basically I am stuck.   Their suggestions:

1. Pay off the phone (owe $650 and would lose all incentives)
2. Pay $10 / day for their international roaming ($300 month * 6 months = $1800)
3. Buy another phone that is unlocked and use that while there.   $300-$500 for a used, phone AND, AND I still have to pay for service on the current phone even though it will never be used.)

They make exceptions for those in the military and I want to know why they can't for college students studying abroad.    I am quite sure this is a common problem which Xfinity turns a blind eye to.

Any different solutions would be most appreciated.   Thank you very much!