Online service is terrible

I have had the worst experiences with Dischem online store. I placed an order on the 26th March 2018 and expected delivery on the 4th April due to the holidays however on the 4th I had not received my parcel. I called the customer care line and was informed that someone would call back. On the 5th I had to call again as I had received no response and was told that it would be out on delivery the next day. It is now the 9th and I receive a call from the call center informing me that I will be missing a product from my order. When I asked if they had tried to source it from one of the stores I was told that all she can do is refund me. I had to request that they check with the store closest to me if they have the product for me to collect. This is not the first time this has happened as when I purchased a Fitbit in your online promotion I was called 2 weeks later to confirm that you are not able to get what I want. Why is it that Dischem advertises product in special online when they do not have the products. It is extremely frustrating when you have paid for something and you receive terrible service.