I confirm it too. Jazz is definitely using IPv6 in Faisalabad too. I don't know what Zong is doing now? Have they too lost confidence in Pakistani market? No innovation, No advancement, No VoLTE whatsoever. They are on verge of becoming second largest telecom operator yet they behaving like Telenor now.It does. Not surprising that they're using dual-stack, but at least they've started rolling out IPv6.
Nayatel (while not a mobile telco), has also started rolling out IPv4+IPv6 (dual-stack) by default now (previously it was only enabled if requested).
I remember I had Galaxy A50 in 2019 when I got an update after which Jazz sim started showing VoLTE option and after that Jazz started rolling out VoLTE after a year. In same update Zong sim also started showing VoLTE option in sim settings. That means Zong have support for VoLTE in Galaxy AX0 and later devices. But still they have not make VoLTE operation on their network. That is too disappointed.