Mondo accumulating admin fees for no services rendered

I ordered a Telkom data deal in September 2018 over the phone with Mondo. I was charged the admin fee and was told my order would arrive within 7-10 days. I queried the delivery 2 weeks later via email to a non-responsive customer sales dept. Eventually after calling and sending a second mail I was informed that the modem was out of stock, and they were not sure when they would receive it. I decided to wait for stock thinking it would be another week or two. It is now November and I have not received anything. my email queries on the progress of the order has gone unanswered. On Monday I sent a mail confirming I would like to cancel the deal order as it is now seeming less and less likely it would come before the development and roll out of 6g if at all. Surprisingly they rep**** fairly promptly to the cancellation mail to confirm the application is cancelled. I was then informed that the service charge is non-refundable. Now the deal was popular enough to have sparked interest beyond the stocking capabilities of this company. If all those service feed are non refundable this equates to R15 000 per 100 people. Money charged for no service or products rendered. If stock was the issue, how were they still selling a product they could not get stock of. What are the legalities around selling a product that cannot be supp**** if a service fee is charged. I am willing to take the lesson of my contribution to their revenue generation for trusting a telemarketer just once, but, I would also like to know what are the repercussions stopping anyone from starting a revenue generator that sells items it cannot stock and keeping a transaction fee when cancelling. I will stick to strictly online where the T&Cs are clear and legible.