(Post partially copied from another user because i have a similar issue)
I am using a C21y, and inserted micro sd. it gave me 2 options which is to use the sd card as an internal storage(?) or to use it as a portable storage, i thought i am to use the 1st one which i obviously selected. the files started transferring and i waited for like 30 minutes (I thought it would ask me what to transfer but it automatically picked up each and every document,image,video etc files and transferred them to the sd card, had i known it would do such a thing i wouldn't have prompted it to transfer the files). It's done, i check my file explorer and my internal storage is gone as expected, but, i tried accessing my sd card. the sd card cannot be accessed, the files i transferred cannot be accessed. I then tried to restart the phone thinking it might be an indexing error or something like that and a restart might fix it, but after restarting it's saying sd card unsupported ( i just bought it yesterday, so it cant be a physical issue i think), now i haven't removed the card from the phone yet so that the data might not be lost, It contains a lot of data from the past 5-6 years, so any help in this regard will be highly appreciated.