Undelivered order

I placed an order for a calculator on the 30th of April. I got a confirmation that the order will be delivered 7 May, it wasn't delivered. I emailed the company Takealot about my order, I was told to redo the order as there was a mix up with my address. I placed the order again on the 12th May, paid for it, got a response that it'll be delivered 18 May, I still have not received it. The frustrating thing is I need my calculator for school purposes, I'm writing exams next week.