Could be a ploy for you to use their postpaid service. But of course this is just my wild guess. Similar to how Maxis VoLTE is available only to Maxis Postpaid and to certain devices only. Then again in the case of VoLTE, eventually Maxis and Celcom will have no choice but to fully enable VoLTE as 3G is to be shut down end of next year. During the early days of Digi VoLTE roll out, there were many problems too. But now Digi VoLTE works even on standalone modem that supports VoLTE. So I believe both VoLTE and VoWiFi will come to all Maxis customers eventually, they are just buying themselves time.

want to ask....
Internet plan still can work if sim no more active?