Refusing repayment of duplicate transaction.

I bought goods online, and returned some of the clothes on 09/01/ 2015. I also purchased new items and all of this totalled to R494.95. The lady who helped me was new, and she told me the payment wasn't successful, and she took payment again. I received 2 sms's confirming that payment was taken, and when I raised my concern regarding this, this lady assured me that they will automatically reverse the duplicate payment. I believed that they will do as i was told and did not follow up on this immediately. In May 2015, I noticed that no refund was passed on this. I visited Festival Mall on 25/05/2015 and spoke to Busi Ezeji. She phoned the bank and said they cannot help in this regard, as they only keep 3 months of statements, and suggested the contact the people responsible for MRP's cash books. As I was there after 5pm Busi couldn't get hold of anyone and asked that I visit the store during working hours. I visited the store on 10/06/2015, and Busi contacted the people responsible for MRP's cash books. They said they will get back to me in this regard. No one has contacted me, and I feel ******. WHY would I make 2 purchases on the SAME day to the value of R494.95. I need my refund!