Pick-A-Part

I recently called Pick-A-Part to see about purchasing a motor and what their policy(s) were if there was a problem and had to be returned. I was told I would get a full refund if I had my receipt and it was within 30 days. I bought and paid $350 for a motor at which when installed was bad. It was brought back 13 days later. I was refunded $215. $135 was kept because they said it was for their "labor". I was unaware that of this as when discussing their policy by phone it was never mentioned. I feel they should honor their word and I should be reimbursed $135.