How do i get a name change? and could i get a last name?

[Rolig Loon]

IF you are a corporation, and IF your proposed last name is the name of a corporation (Like IBM) and IF you are willing to pay $500 a year for the name, then you may apply for a custom corporate name.  Otherwise, you cannot get a last name.  In any case, you cannot change the name on an account.  Each account is unique, and a name and UUID are set at the time that the account is opened.

See https://community.secondlife.com/t5/English-Knowledge-Base/Usernames-and-display-names/ta-p/700173

[Rolig Loon]

IF you are a corporation, and IF your proposed last name is the name of a corporation (Like IBM) and IF you are willing to pay $500 a year for the name, then you may apply for a custom corporate name.  Otherwise, you cannot get a last name.  In any case, you cannot change the name on an account.  Each account is unique, and a name and UUID are set at the time that the account is opened.

See https://community.secondlife.com/t5/English-Knowledge-Base/Usernames-and-display-names/ta-p/700173

[Lindal Kidd]

As Rolig says, you cannot change your username.  You CAN add a Display Name, and that may be in form of a first name and a last name.  

As a matter of historical interest, the naming system used to be different.  Up to about two years ago, when you registered, you picked a name from a list of last names, and added a unique first name.  That became your user name.  The Display Name function did not exist.

So, when you see someone with a user name like "Lindal Kidd" you know the account is at least two years old.