Essentially, if you ran the NPC and got an estimate you find doable, and the early ED FA offer doesn’t match that, you should 1° first, call/email financial aid and ask about the discrepancy: perhaps there’s something they’ve misevaluated, or perhaps you can bring more information to light that they can review then 2° if it still doesn’t align with the number you’d got when running the NPC, then you can withdraw.
However you shouldn’t apply ED if the NPC indicates the college won’t be affordable.
Note: any PHD program worth going will fund your child. If they’re not funded, they should NOT go. The issue is med school and law school, where funding is the exception, not the rule, and never “full”.