I've been using the same (free) account for three years and never changed my username or password. Today I opened spotify only to find out that I've been logged out and when I tried to log in it said that I'm using invalid username or password.
After few tries I gave up and created a new account but this time my username changed itself to a combination of 25 different letters and numbers. (I never connected my account to facebook or anything.)
Is it possible that the same thing happened to my username on my previous account and if so - is there a way to fix it?