I ordered a pedal position sensor for my kia, when...

I ordered a pedal position sensor for my kia, when the weekend came I could not get it to fit and had to schedule an appt. with a mechanic to have it installed,2 weeks later the mech. also could not get it to fit and discovered it was the wrong part. A week or so later I went to the website to get a return authorization and was not allowed to fill out the form as it was over 30 days! What am I supposed to do with a $75.00 part that will not fit my car. It was never installed or plugged in and was sent to me because of your error!! THANKS ROCKAUTO