I took my time machine in for its millennial checkup and service last week. And I still have no idea how much I’m out for it.
They told me they could tell me how many hours it took to do the service, or their rate per hour, but not both!
Now, really!
Don’t you hate it when that happens?
Have you considered that they may have confiscated your time machine? You haven’t had any agents show up on your door, have you?
Or maybe these mechanics tried to use a Schrödinger Diagnostic…and accidentally broke your device.
I started out in Quantum Mechanics, but then I found out that auto mechanics paid better so I switched majors.
One way to resolve this is with a vial of prussic acid, a steel box, a geiger counter and a…a…I forget what. Never mind.
Here’s what you do: argue that since it’s a time machine, and it’s yours, that however they argue, and however they stall, in the end it will always be still under warranty, and they’ll fix it for free.
Why didn’t you just take it back to a time before it needed service?
I’ve reported my Quantum Mechanic to the Cats’ Protection League. Poor animal looks half-dead. 
And here I was expecting some poor physics student, wilting under exam pressure…
Just invest 1p in their business in about 10,000 BC and claim that you’ve already paid your bill through compound interest. No problem there.
The glass is always half empty with you!