18days and still waiting for money reversal

We've book a car at Avis Cape Town Airport, dropped it off 28 March 2015 as agreed, they've told us the money will be reversed in 7days, we've phoned again they said be patient. We phoned again they told us to wait or go to the nearest Avis branch to fill out a form. a form for what? 18 days later and absolutely no feedback from anyone at Avis, very disappointed and will never make use of their service ever again. How long do we have to wait...the amount is about R2000.