I can use my Apple ID via browser but devises still locked

It been around two months that I have received an email saying that my Apple ID password has been changed. As soon as I got that I have done everything I was required to do but since then the account is blocked. Now on my old iPad a new iCloud account shows up and I am asked for verification whereas it’s not my account, it’s a different one. On my other devices this iCloud does not appear but they are still connected to my iCloud but of course still blocked. I can access my iCloud and manage my Apple ID via my pc or even via my phone if I put different account. I can also access iTunes (whether via pc or old iPad but not the phones). I am really confused especially that I have the password and I have the phone number and I have the email!! What do I need to do because am really frustrated and how can someone change my password without any prior notification! And how come a new iCloud account shows up.