Nuisance Phone Call - What should I do?

Mods, not sure if this is the correct place but it is somewhat related to consumer issue. Feel free to move accordingly if there is a more appropriate category.

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OK a bit of a long one but bear with me. It is not a scam (I think) but at the same time don't know how to properly resolve either..

Ever since end of last year, I have been getting calls on and off from a fella call Denise (female name but male sounding voice) looking for his son Conor. If I have to guess, he may be in the elderly category. Sometimes he calls from the mobile but often I get calls from what seems to be various shops/services around the city looking for his son Conor. Even if I tried to block his mobile, it is of no use as various shops/services would just get through anyway (I can't block all the shops they go to).

I did speak to him one time at length few months ago, he explained that Vodafone have messed up and the number his son has, was incorrectly given/assigned to me (I know this is impossible because I have my number for more than 2 decades). He said he had previously made a complaint to Vodafone before and got some credit compensation before. Basically he is going to go to Vodafone to complain again (Doesn't seem like he has because he still calls and tell me about it whenever I said I am not Conor).

I previously proposed a solution for him to try. The solution was for getting his son to call me on my second mobile number whenever he manage to get hold him. My number is the same except just a different prefix (example: one number is 087-1234567 and the second one is 086-1234567). Back in the day before consumer get to keep their number when porting to another provider, different provider would try to entice people to move to their network and you get to keep your number but get to change to their prefix, this is how I have two of the same number on two different prefix for clarity.

The solution proposed was simple, just get his son to call me on the second number (since technically if his son have my same number, he can't dial himself). That way I can verify for sure what number he has. He refused and said he pays for his phone credit and that he has no credit. We left it at that.

I managed to get a surname when one of the shop called and ask for him in full name. I also managed to pinpoint roughly the area Denise is at (Rathmines/Ranelagh area) based on searching the phone number of the shops that he asked the shop to call me from.

I am starting to think that he may have Alzheimer or dementia of some form. While that is a tragic event if it is true but at the same time it would help if I don't keep getting calls once or twice a week looking for Conor. So internet, what do you think I should do to resolve this?