Corrupt File Backup

I've been having problems with my iPhone 6 plus. Last night Apple Tech Support, after trying several things instructed me to back-up my data on iTunes and then do an iPhone restore. After the restore they instructed me to restore the back-up file to my phone. I tried doing that but was given an error message saying the back-up file was corrupted or incompatible. It is not a compatibility issue. I updated the phone to 9.3 and that was successful. Then, still having issues, I called Tech Support to help me. So, the phone and back-up are both 9.3. How can I recover my data, 7 years worth, from this "corrupt" back-up file? Not a happy camper. I find that Apple Tech Support is not very good beyond a few standard fix suggestions. Why aren't you told before wiping your phone clean that the back-up file may not work. Apple should not assume that every customer "worships" them and knows every detail about every Apple product. If there is the slightest chance data could be lost you should be told...allowed to write down a few things, transfer photos, etc. Needless to say I've already called my attorney.