As an ex-JW, I personally think you are wasting you’re time.
The JW’s are not calling on you because they are interested in Catholicism, or because they want to hear what you have to say. They are calling on you because they want to recruit you into their ranks, and the fact that they have called back is an indication they believe you are someone who is receptive to their message. Placing literature with someone is something they see as a sign the person is interested in their teachings, despite any insistence on your part to the contrary.
JW’s are also greatly discouraged from calling with people who can make a good defense for their faith. If you do this when they return, it may be the last you see of them because they will realize they are fighting a loosing battle. It is also likely they will come away from your door believing they made a good defense for their faith, gave you really good answers and used their scriptures well despite what you may say.
JW’s will also call on anyone who takes their literature and engages them in Iconversation due to the fact that they are usually met with at best apathy, if not outright antagonism. They don’t encounter a lot of ‘interested people,’ or have a lot of what they call ‘good calls.’ t is also their practice to make a record of you’re name and address as an ‘interested party,’ if you engage them in discussion and accept literature. They fill out written ‘reports’ every month, stating how many hours they engaged in door-to-door work, how much literature they placed and how many ‘return visits’ they make. It doesn’t look good if you haven’t placed any literature or don’t have any ‘return visits’ to write on your report. The greatest achievement in the JW’s is establishing a regular bible study with someone and getting them to the meetings. If you get baptized into the JW’s people loose interest because you’re sorted. Meaning, when they get someone willing to talk to them and take literature they are inclined to hang onto them. When I was a JW, names of people who would invite you into your home and make you tea were kept for days when it was raining which happens quite a lot in Ireland.
The only way you’re likely to make any headway with a JW to me, is if they having doubts anyway. They won’t admit that, but who knows, one of your ladies may be having doubts and you may plant a seed that could grow. It’s your call whether you think it’s worthwhile or not. I just wanted to let you know how they operate so you can make an informed decision as to how you approach it.