Incorrect Product delivered and poor returns handling..

For the 2nd time in a space of 2 months, I have placed an order and I upon delivery, the wrong item is in the package. This time around I ordered a Samsung product, but received a Xiaomi product that is half the price of the Samsung product. When submitting a return, I chose for a replacement to be sent to me. But I receive an email stating that once the return has arrived back at their depot and is approved, then I will be credited for the amount of the order. I asked for a replacement NOT a credit. because the product that I ordered has since gone up in price and therefore the credit will not cover the updated price. Nevermind the fact that the delivery has taken over 10 days to get to me. And furthermore that it was intended as a birthday gift which is now severely late..