Unknown devices on my Google account.

[silverweb]

This morning, I was doing some Google account maintenance and discovered that there are two T-Mobile smart phones called OnePlus on my list of devices. I have never used T-Mobile (I use AT&T) and have never had a OnePlus phone (my last and current phones are LG), so I have no idea how these came to be linked to my account.

Both phones were registered within two days of each other in November 2018. That's the last time one of the them was used and the other was last used this March. I tried to delete them, but cannot; "update" and "cancel" are the only options in "edit," and "update" doesn't show what it's done.

The help section says that in order to block or delete them, I have to upgrade to a pay version of G Suite and, as administrator, "notify users in your organization that you are going to manage their devices." There's no organization here, just me.

This has me pretty freaked out. How could someone add phones I've never owned with a provider I've never used to my Google account? I'm afraid my account security has been compromised. Can I find out who owns/owned these devices and how do I get them deleted without paying for G Suite?