Hello! I’ve seen similar posts but none of the suggestions have worked for me, such as creating a character on my old realm, clicking through realms etc. I first started playing in ~2008 and I have used the same gamer tag. I started playing again ~ 2010/2011, and my character was there. I reinstalled and paid for a subscription but I can’t find my characters now. I am almost 100% I’ve never used a different email or battle tag. Please help!! 
The license you are currently on was created in 2014, so it would seem you did have multiple accounts at some point.
You didn’t provide any character names, but based on my own investigation, if I had to guess I’d say the account you are looking for is a Battle.net account attached to an email that is based on your current BattleTag. Under an @gmail address.
Assuming you’d rather play on the other account, you may want to put in a refund ticket to see if you can get a refund for the recently purchased game time. These things tend to be time sensitive. Let them know that you reactivated the wrong account by mistake.
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