I've inserted the SD card where it's supposed to go. But the moment I turn on my device with the SD card in it, there's a notification saying "Can't write to SD card". And when I go to Settings -> Device care -> Storage -> Advanced; it says that my SD card is corrupted and that it need to be formatted which would mean losing all the data I have there.
@EmmaFabry: Sorry to hear that you're experiencing this issue. If your SD card already has data stored on it, and if you have access to a home computer, then please backup the contents of the card, then format it in your Galaxy A7. I understand that this isn't ideal, however formatting will be required in order for the card to function as intended. If you're unsure how to format, please head to Settings > About Phone > Software Information, and let me know your current Android version, and I can point you in the right direction.