Cancelling order to increase price

I have a serious problem about how Takealot is handling this order. I made an order for an item that is available and in stock. Few days later I got a message to say they could not deliver even though I selected a collection point in Boksburg. To make matters worse I got a credit of R158 instead of what I paid for which is R193. Is there a reason I am not getting full credit of R193 as there is no grounds to withhold R35 for delivery as you did not deliver anything. The same item I ordered is available today for R293 which is a full R135 more than what it was last week. This is unacceptable and border line *****.