The worst case is that you already paid your time building upfront. In this case, I would talk to the person who sold you the package or alternatively simply pretend that I don't understand what they're doing and file a flight plan the night before. Or I'd fly without a flight plan as long as you don't cross borders or fly through an CTR. In places like Hungary, flight information nearly always asks if you have a flight plan, but they also help you if you don't have one. While talking to your time building provider, you can also mention that you would be willing to disclose their name and practice to the public (e.g. Pprune, Google and other relevant forums). If you have a legal insurance or the means to pay for an attorney that's also an option.
If you haven't paid for the remaining hours yet, I would definitely look for a different time building place.