2 or 3 days ago, i dropped in to their service centre (orchard) to ask same question. the guy said they were instructed by IMDA to remove it to encourage people to switch to 4g phones. Then added very dismissively, "anyway now dun need, since everyone got 4G or 5G phone".
he could not understand that the telco makes a decision whether to support the phone or not. VoLTE is a necessary but insufficient pre-requisite, if a telco does not support it, it does not mean the phone is not VoLTE capable.
i pointed out it had nothing to do with 4G, since it is a point-to-point VOIP app, and can even work when phone does not have the simba SIM inside it. he just shrugged and said, "Just buy a new phone."
@ibrahim Noorali for now you can download the app from simba website. search for "voice app"
to me, this removes 1 of the 2 reasons to keep my simba line (the other reason is backup roaming SIM).
(for me, local use, the coverage and speed is really cui, so that is a huge negative)
the app is necessary for countries which may not support my phone.
whether it is true or not that IMDA asked them to remove it, i dunno and can't prove it either way.
anyway, will keep a local copy of the APK in case i factory reset my phone in future.