DD new to what's app, but already in groups and has messages??

[TweeBee]

Hello,
My DD has just got a new smartphone and has been keen to join what's app as we have family chats on there. I've just downloaded what's app and put in her new number but when I opened it there were already a load of groups as though she was in them.
I know it's not her because she's only just got the phone number and some of the groups last had messages in 2019 and called things like "boys school name (never heard.of school) y7".
This new number is on a SIM card from a company who are meant to be the go to for worried parents starting children off with technology, but could it be that they are reusing a number and these are groups the previous person was in?
Or what can it be?
Thanks

Yes could be a reused number - DP (who is not called Dennis) gets calls for 'Dennis' regularly even though he's had this number for a few years now. Just leave all the groups and delete the chats.

I'd feed back to the company and try to get a 'clean' number.