Welcome! A couple things.
1) Only the profile manager can change the LNAB (last name at birth). You want to message him from the profile page (the little envelope).
2). When you message the PM you must send him a source for his LNAB--birth record, baptismal record, etc. Just messaging a PM and saying his name should be . . ., isn't sufficient. How do you know that is how he spelled it?
The PM may have it wrong, but it you show him why it is wrong by posting the evidence under "Sources" then messaging him, he may change it.