Hi SamB1980, thanks for posting and welcome to our community.
Sorry to hear you've not been able to activate your call waiting feature. Because of the code you've mentioned keying, it sounds very much like you're talking about Virgin Mobile. If you've already tried this with both WiFi and mobile data switched off, then I'd like to take a closer look on your behalf, to check if it's showing as active from our side. I am going to send you a private message. Please look out for the purple envelope in the top right of your screen.