VoIP for parents: value, anti-spam, and simple?

My parents are currently paying $80 monthly with AT&T for their landline. They don't make many calls generally, and only call internationally to Canada. Aside from the price, their biggest complaint is the amount of spam calls they get.

Personally, I just switched to Voip.ms and love it. But it's way too involved for them to set up. I'm afraid even if I would initially do so for them, there would be many more follow-up requests. And I'm not looking for an ongoing tech support project.

Which VoIP services offer (priorities in this order):

1. consistent and reliably good call quality
2. effective in reducing/blocking spam (without requiring geekery)
3. super simple to configure, requiring zero tinkering going forward
4. inexpensive