In the context here "work on" is incorrectly used. "work" is often followed by "on" when we refer to something specific.
I'm working on a new project at at moment and it's very interesting.
I need to work on my English as it's very poor.
My brother is working on the car at the moment as it has a problem.
In these cases the sentences are incorrect if you don't use the preposition.
I can't imagine any situation where you would need to work on your Visa card unless you needed to apply for it or there was a problem with it that you needed to resolve.
p.s. What does "work on" mean here [U]not[U] What's mean "work on" here?
Don't forget the auxiliary verb when asking questions!
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