Called this morning. It looks like they're still active. I got two other spam calls within a few hours today. I think these companies just try to see what numbers you might pick up.
I have also received 6 calls from this number since Monday. Not a single message left. Thankfully they added the call block option on the new iPhone, I am done with this annoyance.
This number left me 8 missed calls on my phone within one day, and of course anyone who'd encounter this kind of situation would pretty much be pissed off. So i tried to call them back to ask them what's their concern, one of their customer service representative answered the called and it turned out that the number belongs to a company who specializes in Solar Panels. They said the main reason why they called is that they were just assigned to call people because they're trying to reach homeowners so they could like pre-qualify the homeowners for their Solar Program. So what i told them is that i'm not interested and asked them to stop calling me. Then boom, problem solved. They said they will immediately put my number on their Do-not-call list. Maybe they got shouted at by angry people already because bombarding phones with missed calls and calls without responses would really be irritating. Kudos for their politeness though