Mr Price sport complaint

I ordered a yoga mat from MrPrice sport in July 2020, along with dumbbells. I receive a partial delivery as they stated that the yoga mat was out of stock. I expected a credit amount on the item out of stock but that did not happen. I subsequently sent them two email requesting a resolve on the matter, till today they have not responded or refunded me, it is currently September 2020. I am disgusted by this behaviour that such a large retail store could take advantage of the situation just because the item is of a small amount.