Questions with onstar in a 2023 Buick Encore

I have a 2023 Buick Encore and when I purchased my vehicle thought I had onstar for a limited time, or so I was told.  Thought it was for three years.  Yesterday my onstar system started talking to me saying something like “onstar is on” or something like that.  It has never done that since I’ve had the car.  I checked on “my Buick app” and it says I have onstar for free until 2033 and I have no idea how I have that.  I was told it was free for limited time then I’d have to purchase a plan after free on expired.  My questions are…  How can I find out which plan I have?  Why would my onstar just start speaking to me without being prompted?  Could someone else have updated and paid for additional service and how would I find that out?  Thank you