Filing a request to CS Chat through Maxis app seemed to work for me. Was surprised VoLTE status today after 7 days from the request date.

I did get them to consider escalating my request since had been a long time Maxis user, >15 years.

They didn't promise timeline on VoLTE activation and remained the same 'will be activated by batch' statement.

Main line was on non-VoLTE phone until recently, 1 month back. Subline had VoLTE activated without a request.