Not honouring full value of voucher

I received a R75 voucher from Truworths and I decided to purchase some items on my account.<br> <br> I returned one of the the items. The full price was R 380, however the refund was only for R351.47.<br> I queried this with the cashier and she said that it was because the item had been discounted. I then noticed that the R 75 voucher had been split 1/3 against each item purchased.<br> But was told that the full R 75 would be given against the 2 items remaining.<br> Of course this is not the case. I phoned customer services and was told that is how Truworths handles this type of voucher.<br> Now my question is how do you offer R 75 discount but in the end only give R 46.47 against the total remaining purchase of R619?<br> Whilst the amount is neglibilge the principle is rather skewed.<br>