How to change an incorrect family last name?

We have a fairly new young family in our ward. When the membership records arrived they are listed with an erroneous last name. The records include their complete correct names with this wrong last name added to the end. They say that they have worked with ward clerks and helplines from headquarters with no luck. Our clerk says that he has tried and been unsuccessful and does not want to mess with it any more. What can be done to fix this error? I am their assigned ministering brother. Thank you.

Tell your clerk to click on the Household tab and edit the family name there. Failing that, he needs to contact the GSD either by phone or by message.