Improper Credit Practices

While I was employed part time at this store I purchased some items on 02/21/08. I then returned 2 unused, undamaged items on 03/10/08. The store manager processed my credit. I then resigned from the job and returned my key. The owner proceeded to void out this credit that evening so it was never credited to my account in addition to NEVER informing me of this. When I complained to the headquarters I was told he told them it had been more than 30 days since I purchased the product, it was only 19 days. This return policy is known by everyone and is also a requirement ordered by the headquarters so that they may be a "Gold Medallion" studio. He is taking my resignation personally. He also told the manager that "employees purchasing items at the discount of 50% were not entitled to return product" but that he WOULD DO IT THIS ONE TIME. The manager's name is Jill 214-909-7689. I NEVER saw or signed any kind of employee handbook stating this policy, I was never told this, and in fact I have returned other items previously with no problem whatsoever.