I'm sorry your providers have so unhelpful. Unfortunately, your experience is not uncommon.
Whether your machine is transmitting data (limited data via cell phone) is an independent issue of whether the machine is writing data to the SD card. The only way for a provider to determine that the SD card slot and SD card are working properly is to physically take your machine and test it. Mentioning OSCAR probably just gave them an easy out to dismiss you.
You need a bigger hammer. I recommend you install ResScan -- a ResMed software product that will read the SD card from your ResMed CPAP machine. You can get ResScan (version 5.9 recommended) on
Apneaboard.com. Try importing the SD card into ResScan. If it fails, as I expect, then your complaint to your provider is that ResMed's own software product will not read data from your ResMed machine, which makes the problem fall squarely in the provider and ResMed's laps.
If by some freak chance ResScan works but OSCAR doesn't, then come back to us with that information. I truly do not expect that situation to arise, but if it does, we're the ones who will need to respond.