I would suggest sending a demand letter to Meta's legal department offering to settle for somewhat less than $1500 per violation. Here's an example: https://www.junkfax.org/w/images/0/0b/SampleDemandLetter.pdf
If they ignore you, be prepared to file a local case in small claims court (which you can do yourself without an attorney). The court can force them to pay you if you present evidence of the calls and the law(s) or regulations that were broken.
Disclaimer: I am not a laywer and this is not legal advice, but I have collected money from TCPA legal settlements in the past, each without needing to go to court.