AMAZON disgruntled

I purchased my wife her first kindle about 8 years ago, unfortunately it became faulty and we could not find a dealer to repair it so I purchased her a second one. She loves it but I have forgotten the account and login details to update the credit card details. I have been struggling now for about 18 month to find someone who can assist me successfully with this. They are quick to take your money on your credit card and say that a technician will call you and talk you through it but, allas back up or follow on service is non existent. Excellent device but that is where it ends.