So, I created a free account and played till lvl 3. I liked it so much that I downloaded the beyond 20 app and bought the subscription, bundle plus extras. I now have the problem that when I am in the group that I started with I can only use the free account, even though I created the exact same character as the free account. Bottom line is can I merge the accounts?

Thank you

There is no "free account " and "paid account" on D&D Beyond. An account is just an account. There would be no reason to create a second account to buy things. If you've created two accounts, and in a campaign with the 'wrong one' just copy the join link for that campaign and then log out, then log in with the "right" account, paste the join link in your browser and add your character. You can then use that. You can go back in on the wrong account to remove that character, and you're then free to continue using the right account/character. So there's no reason at all to merge accounts.

D&D beyond is not connected to Beyond20 at all. Beyond20 is a browser extension that was made by a 3rd party. It's not an 'app' and doesn't require accounts and it's free. 

Thank you