Samsung account linked to old phone

[caromul]

Having issues with my Samsung phone account. It seems linked to a friends old phone I used for a while. So I can't change it, as not same as my email and password. 

Security issues... help? Also anyone know if my phone been accessed, after I had Google code text when not asked for one

THANKS IN ADVANCE 

[Piper123]

Log in to your Samsung account and remove the erroneous device.

If you can't log in, you'll have to contact Samsung Customer Service and seek their help to get you back into your Samsung account.

[Daz73r]

Go to my devices and remove it