As far as I can tell, the credit card company can do very little in this case. Any dispute that you raise with them and they in turn with Mastercard/their corresponding bank is a duplicated effort for the dispute you raise with Instarem directly.
You could try talking to the retailer too, but at least in my experiences, the retailer always says that their bank will talk directly to our bank (Instarem in this case). Or that if the transaction is cancelled/refused at the point of sale, it may take a few days but whenever that it does get processed, the funds will be returned to our bank.
I agree that an interim status update based on where the transaction is or the funds are would be useful, but I suspect that the Instarem's own system doesn't update that often.