R CMD check warning: Functions/methods with usage in documentation object ... but not in code

The \usage section in the Rd file needs to include the following:

\method{names}{surveydata}(x) <- value

If this is not automatically inserted by the @method line (I presume that will only add \method{names}{surveydata}(x)?) then you need an explicit @usage section that includes the above. Something like

#' @usage \\method{names}{surveydata}(x) <- value

I would also change the @name and @alias sections to refer to the method explicitly not the generic as that will clash with the Rd file in R::base.

Essentially, the warning is coming from the fact that your package doesn't contains a function "names<-" yet you are using this in \usage{}.