Takealot.com Sales Assistants Cancel Order Without Given Permission

I have had amazing service up until total. I purchased some items and paid for them. In my error I selected an incorrect battery. I sent a request to takealot.com and was told that I could not exchange or swop the item. I then sent a follow up email only asking how I go about canceling my order, but not requesting a cancellation. This was then immediately followed up by a full cancellation. To add to that, I purchased dog food with a voucher which we had won, and now that's invalid, and amount credited to be is less the voucher. I think their sales assistant need to comprehend simple english, if in doubt contact the customer...they have my details. Hayden Thumbasamy