Are you talking about internal Do Not Call lists or the actual Federal Do Not Call list? Because I used to have that issue with credit card companies, random loan spammers, and such with both mail and phone call spam. I signed up for the list with a 100% opt-out option and just like it promised, within 3 months, the offers stopped coming in.

That being said, I also try to be pretty careful about putting my phone number out there, taking time to judge when a real phone number is needed or not, and asking pretty specifically for what reason a company wants my phone number and often just ignoring the service if an adequate reason isn't given.

Since I've moved abroad, I have apparently been less careful and I occasionally get calls and texts on my foreign sim, and I must have given my email out as there are suddenly lots of hot-singles looking for me, but it is 100% related to my current region, whereas before my Spam folder sat untouched.

Both really. Companies face fines if they keep calling people after they request to be put on a do not call list so it's a big deal. That's how I remember my experience at a call center anyway.