My mobile system memory is not large enough to down load movies. How can I change the xfinity mobile app to save to my SD card on my mobile device?
if you are running the nougat or orea version you can adopt 'an' SD card as internal non-removable memory that can then be used as if part of the phone's own memory. DRM won't allow non-system memory storage.
Piggybacking off of Rustyben, the app you're using would also need to be able to distinguish your SD card as the default internal memory.
You could download the movie to your computer then transfer the file to your SD card. Personally, I save content to my phone's internal memory then manually move the file to my SD card.
Movies on phones/tablets generlaly cannot be transferred. If they go to internal memory, the app will ONLY look for it there. It's all about the security. Even with Android's ability to add SD memory as internal memory, it may not work as apps can still block using it. Also, for Android, make sure the card has an A1 rating, or it may be too slow. There is a simple app called "A1 SD Bench" you can use to test the speed of your internal and SD card memory.