icloud untitles my iphone photos

It used to be my iPhone named my photos (e.g. IMG_xxxx.jpeg) now it untitles them and when I want to download from iCloud the photos are renamed to 123_1-1.jpeg then 123_1-2.jpeg and so on and it changes the date of the photo to the date of the downloas. This might not be a problem, but I do legal work and the camera IMG name and info is important and I add to folder, which already have these names and have accidentally erased previous photos. I have googled this and cannot find any information on how to retain the originally IMG name. Please don't suggest I rename the photos, because we are talking about hundreds. Thank you in advance