reversal not being processed

On the 10th of march I returned a device to vodacom which I bought online and was not happy with, I was told within 72hrs the reversal will be processed. It was only captured on to their system on the 16th of march. Now 72 more hours have passed and its still not reversed, in a few days they will probably be debiting a device I don't have, now they tell me it take 7 working days which I was not informed of. They want to debit my money where as I do not have the device. Every time I call they keep saying tomorrow and tomorrow never comes.