J. P. Gilliver (John) wrote:

I want to do their systems some harm ...

That would make you worse than the scammer calling you. You become part
of the problem. Until you *agree* to commit some action on your own
computer, they haven't done anything illegal to your property. At best,
they might've violated the Do-Not-Call list *if* you subscribed. Are
you going to ASK them if you can commit harm to their property as
eventually they will ASK you to grant access to your computer or ASK you
for your credit card number? What do you think will be their response
when you ask for access and permission to harm their computer(s) or
telephony equipment?