Some companies have notoriously desperate pesterering. I've opted out of XM Radio and Spectrum solicitation multiple times. It doesn't seem to stick.

You must explicitly use the words “Put me on your do not call list.”

It’s dumb, but “If you want a telemarketer to stop calling you, do not say “Quit calling me” or “Don’t call me again.” In some companies, Reps are informed under strict guidelines to only delete records if the customer specifically requests they do so. Telemarketers are only required to put you on the “Do Not Call” list if you SPECIFICALLY request to be put on it.

https://consumerist.com/2007/08/27/to-get-telemarketers-to-s...

Again, depends on the country and the laws of that nation.

I'm Canadian: https://crtc.gc.ca/eng/phone/telemarketing/reg.htm

you don't need to use specific terms and they have 14 days to stop calling you. in my case they continued to call and so i used the "complaint and enforcement" numbers on that page and reported them.

have not been contacted since.

Ahh, I thought XM was a US only company but they apparently only cover US and Canada.

As i posted above, if you are in Canada you can file a complaint with the government. This is how i finally got them to stop.