Am I using "gsub"correctly?

I am trying to replace all the "." in a specific column of my data frame with "/". There are other characters in each cell and I want to make sure I only change the "."'s. When I use gsub, I get an output that appears to make the changes, but then when I go to View(), the changes are not actually made...I thought gsub was supposed to actually change the value in the data frame. Am I using it incorrectly? I have my code below.

gsub(".", "/", spy$Identifier, ignore.case = FALSE, perl = FALSE, fixed = TRUE, useBytes = FALSE)

I also tried sub, but the code I have below changed every entry itself to "/" and I am not sure how to change it.

spy$Identifier <- sub("^(.).*", "/", spy$Identifier)

Thanks!