I tested their API tool in January for literally no longer than a day, I told them no thanks and I don't want anything to do with it.
I then used the same FB account with another APi tool. and magically all the spend from my account is being accepted as if I am using their tool (which I haven't touched since)
now I somehow got an invoice for 1k and they say that I signed something and I owe them, and they will put legal action if we don't pay.
I don't like their business model, piss off clients, then expect to be paid for nothing...
I think AdrianM had a similar story from them?
Did you got to you app settings and remove their app.... because otherwise their app would still be integrated with all your advertising. Though you should be able to argue they can look at their login logs and see you haven't been logging into their platform at all and that not removing the app was an oversight on your part.