[Mr.ac]

I really don't know what to tell you, since the car is at the shop. Or is it? Can't tell by your writing. Sounds to me like you got air in the system. That really fucks with abs units.

I would tell them to road test it. If they still have it.
If you have it check the pads, and change out the brake fluid and bleed it good. The only real way to test it is to brake hard. You can do that pretty safely with low speeds. Then work your way up higher. Just make sure your at an empty long stretch of road.