Not a problem, I am sure they will return your call.
In the meantime, you might want to double and triple check all the wiring. The 24V reading, is what C-Com is reading from your ECU, even though only 12V maybe applied. The main problem with it is either power supply or processor chip inside the ECU. Pricing to fix the issue will probably vary depending on what they find.
Now the original problem could be a wiring issue, or not. But to make sure, I would check the wiring good. All grounds and power. Make sure you don't charge or jump the battery with ECU plugged up, and don't weld on the car with the wires hooked up to the ECU. This can do some serious damage to the board.
I have seen some of these issues in the past, and some seem to be easy repairs, while others take some time. Regardless, I am sure they will find something in the box, just a matter of what and what caused it.