I'm in the progress of making my own clean neighbourhood for The Sims 2 for the first time. Today I finally finished creating townies and I changed all their surnames (since I made multiple at once with the same surname). I used a tutorial from simswikia since I am new to SimPE and changed them 'correctly' or so I assumed. But now, when I started playing, I saw a few of them walk by and noticed that they still had their generic surnames. I've checked SimPE again and there their names are still as how I wanted them to be.
Is there some sort of explanation of how this could be possible and is there a solution? I know I'm a SimPE noob but I'm willing to learn from my mistakes

All you should have to do to change their surname is open the "overview" tab of their character data and type the surname in the second field. Did you commit and then save?

If your game is not using US English then you need to make the change for the language your game is using or the change won't show in game.

Yes I did

Yeah, you're right. I corrected them for Dutch and now everything seems to be fine. It's stupid that I haven't thought about it earlier but thanks for the tip.
(Although my neighbourhood seems to be filled with mean townies since my newspaper gets stolen daily by three different people )