Iphone 6 ma. 5 n 5s tarak dapat.
SE im not sure.

Dun simply put ur statement if you don't know.
U can use volte call to anyone and anyone can call u with/without volte.

The only thing only for volte to volte is better setup time and higher HD voice compared to normal 3G/2G calls.
SE support. Pls go check digi volte faq

http://new.digi.com.my/services/volte
iPhone 7 / 7 Plus
iPhone 6S / 6S Plus
iPhone 6 / 6 Plus
iPhone SE

tarak. only 6 n aboveeeeeeeeeeee

nevermind. 4g or 3g janji boleh call.

All app-only subscribe plan back to normal as well as postpaid online payment

To enjoy these new features, which come at no additional cost, both devices making and receiving the call must be VoLTE-capable with the feature switched on and with both customers located within Digi’s 4G LTE coverage area.
This one? Perhaps the feature is VoLTE quality.
How can a phone will know who he dial is iphone with volte capability or no before reaching them?
Another fact, if YES 4G VoLTE call maxis user now? what should they do? drop to 3G(they only have volte)? call drop?

If you are saying to have volte quality then you are right.

A call B:
A (iphone VoLTE) to B (3310) = the call at A will still VoLTE, remain at 4G
A (3310) to B (iphone VoLTE) = the call at B will still VoLTE, remain at 4G
A (iphone VoLTE to B (iphone VoLTE) = both side will at VoLTE, remain at 4G .. if network stable, it only requires 1s to reach B, same as wifi calling to wifi calling

My iphone 6s plus still remain on 4G signal when receiving call from my friends using android phone from Maxis and Celcom     

But currently the call will be like this.
For example DiGi user with volte call to YES 4G VoLTE

DiGi user --> DiGi IMS -- > DiGi 2G/3G network ---> YES 4G Gateway -- > YES 4G IMS --- YES 4G user
and both side will using VoLTE 100000000% for sure.

DiGi IMS network connects to other IMS network will be real after this, for better call setup advantages and saving TDM costs.
FYI, government previously still forcing telcos to use TDM for interconnection between telcos.
FYI, ZTE is ZTE. Many issues comes due to legacy 2G/3G/CSFB network. I cannot tell more at here
A big wrong.

EPC/PGW detect this when user register VoLTE via different APN (which is "ims" for U Mobile, DiGi and Yes 4G, im not sure whether this is standard APN  for all VoLTE in the world or no). Then phone will perform SIP registration to IMS network.
Calling will cause phone trigger SIP calling to ANY numbers, as long as the number exist (999 and 112 are still pending MCMC standard).
VoLTE and Wifi calling all using SIP call. A SIP call wont check where is the destination or even the destination is fix line, or mobile or VoLTE or no. The call just go through.
If i am U Mobile and U are digi, and u can know my subscriber using VoLTE or no then GG ad lo me 
but end to end HD voice capability can work if both parties agree on this 
For example, DiGi VoLTE users ---> DiGi IMS ---> DiGi 23G ---> UM 3G ---> UM users (who phone support HD voice)
But ... slow slow wait.... government very slow at this.

talking about SIP call,
Did u see any skype call cant reach fix line/mobile phones?
Did u see any voip calls cant reach fix line/mobile phones due to they are SIP calling?
All legacy networks are accepting SIP INVITE and processing accordingly.
Those calls between MSCs and between OLOs are now using SIP protocol too(this one seldom, will implement soon).

And im holding iphone 6. I can call anyone using VoLTE (my signal wont drop to 3G).
And also Im part of the VoLTE testing. Im sure how DiGi core network/IMS network works.
Im not sure bout this... but normal call is 64kbps dedicated bandwidth... i think HD voice is more to the kHz the audio is captured? even though 3G HD voice also got 6.xx kbps

Currently digi maxis umobile celcom using 12.65kbps for HD voice codec bit.... and UM normal call using 12.2kbps... tat is y UM calls will be only slightly difference between HD call and normal call in its 3G network

https://patentimages.storage.googleapis.com...000025_0001.png

I think you can.

My iphone 6s plus still remain on 4G signal when receiving call from my friends using android phone from Maxis and Celcom     

It  can be VoLTE at Digi's end, but not necessarily at the other end.  So a caller on Digi can still make the call over 4G+ regardless of what technology the other end is using, even landlines.

First, VoLTE is a protocol using LTE network to make calls, so no matter you call to B party with or without VoLTE, your own side wouldn't drop to 3G aka CS Fallback. I have question for you, why you can make calls from 3G/2G to fixed line?

Currently, Malaysia only 2 operators launch VoLTE, and you already know that.
Secondly, why VoLTE interconnect not possible? Then how you make calls from mobile network to fixed line network? Why previously can achieve on 3G to fixed line and why now not possible for VoLTE interconnect?
Lastly, I used DiGi VoLTE since 25th Oct night until now, no matter who call me or I make call to anyone, I ALWAYS see the 4G sign still there.