So we are not on Office 365 but have had requests to use Teams to collaborate with clients. As IT I wanted to see what the experience was like before our end users, so I created a new email and signed up for Free Teams successfully and then downloaded the desktop app. However I can not sign in, I chose personal account then enter my password and get hit with this.....
Someone has already set up Teams for your organization
Ask your admin to get you started with Teams, or set up another org in Teams using a different email address.
No one has setup teams for our organization we dont even have an organizational MS account, just a personal to buy office products. I have found this entire process extremely convoluted.
Someone in your org set something up using their e-mail since that's all that's needed to verify basic account setup. I had this happen in my org and ended up using a long tenant name because of it. I think you can call Microsoft to find out who registered, or have them send an e-mail to them and you can check your spam logs to see who gets the e-mail. Usually the culprit is dynamics 365 or someone signing up for PowerBI trial.