Why do the robo calls still continue even after paying for this product?

your carrier control who can call you not the manufacturer of your phone, that would be like expecting your letterbox to eject unwanted snail mail.

read

Avoid unwanted calls on iPhone - Apple Support

and

Block phone numbers, contacts, and emails on your iPhone or iPad - Apple Support

and you can give them feedback using

Feedback - iPhone - Apple

SonofDarkness wrote:

How do I screen robocalls?

Contact the app developer, contact your carrier, and contact your legislative representatives.

I suspect the call-blocking app just doesn't work, as spammers can change the calling number.

The carrier may or may not be able to assist with reducing unwanted calls.

The reps because this is a general problem, and they might encourage the carriers to better address this mess.

I'll often mute unrecognized callers and unrecognized senders, but that's not an option for everybody.

One particular political spammer—not sure if they're if they're the political candidate they're claiming to support, or the candidate's opposition—is recently quite persistent with their spamming efforts, too.

Contact the app developer -

https://nomorobo.zendesk.com/hc/en-us

No idea what "product" you're referring to.

If you subscribed to a call screening service and it's not working for you, take it up with them.