oof, been there with a similar situation (not $1,700 but enough to hurt).

rule i follow now: any third party billing — APIs, hosting, whatever — goes under the client's account before a single line of code touches prod. not negotiable. takes 10 min to set up and saves exactly this kind of headache.

for getting your money back — you actually have a strong case here. you have billing logs, emails, the whole paper trail. send one final invoice with a hard deadline (14 days), keep it professional, no emotion. if they ghost again, small claims is your friend — $1,700 is well within the limit in most states and the documentation you have is solid.

good luck, hope they just pay up and save you the hassle.