your emergency brake has nothing to do with your front brakes. What year car are you driving? Do you have ABS brakes? Did the shop do an inspection of the back brakes or dismantle them? Does the car act or sound like the brakes are on? A couple of things. Check to make sure your emergency brake handle has not been pulled up a little. If that doesn't fix it then find a parking lot with no obsticles and run the car in reverse fairly fast and stop the car using only the emergency brake, that will readust the e-brake tensioner. Let us know.