Glue them on.....hahahahaha everyone knows your supposed to spit on them and get them to stick that way.
I'll admit that is the one big problem in our stores is that not all the staff know everything about every product - like me - I know nothing about car audio stuff. You may have been unlucky and got such a person. Did you take the matter back up with the store? Dangerous advice needs to be acted upon, the store manager needs to be informed.