Paid up loan from vertex and std bank refusing ref

Had a loan from std bnk which was administered by vertex and paid up 25feb2016. Std bank debited my account for an amount f R1500 on 25march2016 and upon enquiry at festival mall branch I was told this amount is for my std bank loan and cannot be reversed as vertex did not pay my std bank loan since november 2015. I contacted vertex where Mampho Sweleni forwarded me my loan statement and indicated my paid up statement has been forwardd to std bank legal department. I forwarded the statement which I received from vertex to standard on the 04th april 2016 to customer service email - [Email Removed] and till today my money has not been refunded back to my account. I contacted vertex again and there s no help for me. When will standard bank refund my R1500.