If you call local authorities to unlock your vehicle, they will likely want you to sign a release or waiver in the event they damage the vehicle. You don’t have to sign the release, but if you want them to unlock your vehicle it’s about the only way to do so.
By signing the release you will likely not be able to sue them for any damage caused to the vehicle in attempting to unlock it, unless they act with gross misconduct (which is generally very difficult to prove). However, most local authorities like the police have equipment to unlock vehicles and are generally good at it. If you call the police, allow them to do their job and hopefully you’ll get your car unlocked without any damage at all.