i changed my number and now i can log into others accounts?

Basically around 3 or so months ago i changed my phone number and when i tried to login instagram with my new number i logged into this random girls number, i've also been getting reminders from an alexa that is connected to my number, so naturally i got curious and tested other apps, tiktok, snapchat, amazon, facebook, messenger, cashapp, and doordash were all easily accesible with this new number into this random persons account, but now im also scared because …

accounts alexa can connected girls instagram log login my number phone phone number privacy random reminders