The Pep Boys

I took my car into pepboys for a wheel alignment. When I left pepboys I noticed that my car began to drift. I thought nothing of it. I've continued to drive my car with the drift and now it has began to fishtail. I talked to a mechanic and upon his inspection he informed me that the steering, drifting and fishtailing was a direct result of a bad wheel alignment. I believe that because pepboys saw that I had a free coupon for a free wheel alignment that they just decided to rush through it. Another issue I've noticed since the alignment was the extreme shaking of the car. I am afraid to drive my car and don't know what to do at this point