Received a new sim card since other didn't work, but struggling to get hold so they can activate my new sim card in order to use my internet

I have paid these guys, sent me a new sim card, still can't use my wifi router since they put you through an agent on their weird WhatsApp chat but no one gets back to a person. Struggle to get hold of an agent, i really give up, I have never struggled so much with a company.