What to do if I created a free account and cannot join my current organization's Drift?

What you would need to do is delete the account currently associated with that email. The reason is that you cannot have more than one account registered to the same email.

The steps to do this are going to settings -> my settings -> account and scrolling down to delete.

Once you delete your current account, mention it to the person responsible for your organization to delete the invitation on their end, and then they send you a new one.

Here is the help document for them just in case: https://gethelp.drift.com/hc/en-us/articles/360019664533-How-to-Add-Users-to-your-Team

Then you should be good to go and ready to accelerate!