Its not a big deal. I was invited to join a PTI whatsapp group here by PM ( Private Msg) too. So I said why not. But turned out it was pretty useless. There was like only 1% talk on politics and the many other members just spamming jokes, memes and videos. And it was non stop. My phone battery would run out by midday due to the non stop notifications. So after a few days I just left the group.
There were no mods on that group, other than who invited me to join via PM I couldn't tell who the others were because obviously they were using different names/IDs than on the forum.