Stillwater Motors Over charged on y auto repair - refused to provide a refund Stillwater, Minnesota

On 07-31-12, I took y vehicle to have service.  I was told by a service rep. that the repair was a General Motors defect.  I was told my share of the cost would be $75.00 to $100.00.

Hours later when I picked up my vehicle I was told the cost was $135.00.  I was never told it would cost that much.  Stillwater Motors had my phone number and never called.  Why?

I asked for a refund from the dealership and I was refused.  I was told to contact General Motors in Detroit.  Strange? I deserve a refund.