Telco can check your phone model before allowing you to connect to VoLTE network (as well as other services), there are few ways to disable this checking, just browse XDA and you'll be able to find them (if you are a tech-savvy person la  )
Most likely, so far I am able to use VoLTE on band 5, 38 and 40, maybe certain places don't have VoLTE yet just like what you said, but VoLTE is quite buggy on my Note8, sometimes need to switch on airplane mode and switch off again to connect to VoLTE on same location and tower 
Only popular models get the support nowadays because VoLTE and VoWiFi (WiFi Calling) both require extra settings from device manufacturer and telco to ensure these technologies can work on their devices.

    Since you are just low usages user, why not just MNP to OneXOX Black B10?
You get 28 months validity and 1GB monthly (rollover) and 20 mins free calls, call/sms is also lower?

Yoodo not able send SMS to 5-digits numbers.
My XOX kept failed to send SMS, but remove International Code is send-able.
Big 4 players don't have TAC/SMS issues, heard some MNVO(s) might got some issues OUTGOING (incoming should be OK).
haha, actually MNP is very hassle-free, can just left old sim with agents and let him/her settle for you.
Otherwise online MNP also very conveniences.

For prepaid they have cooling off periods too? I thought that only apply to postpaid plan? Hmm i guess i'll try to contact the telco. Thanks!

But my Bro GX50 already exceeded 1 months still failed to port out.
Reason: Outstanding Amounts (but all was cleared)

He said checked 3 times, and called U center but was told no ideas with WHY got Outstanding Amounts but all was PAID. LOL!!! Bolehland standard.... Port-in easy, Port-out susah...
(In other U threads saw someone said after port-in U then numbers become them, is that true?)

Anyways, just asked my bro submit official complaint to SKMM and Umobile.   

  Matilah if like this Umobile~
Then I'll asked my bro re-submit port-out and complaint to SKMM in same time, see can break other records mo? 

It seems that Unifi mobile now limits 1 sim per person. And the free LTE data is now reduced to 2GB only.

Do you know HSPA+  can also achieve the same or even better result?

Damn lucky, mine 4G average speed less than 2Mbps.

Ayer Keroh, Melaka.

Aside the congestion, it also depends on how the carrier implements the network.

I can consistently get around 16-20mbps on HSPA+ alone on Celcom at Batu Ferringhi during the daytime.

They need to lower prices since their LTE is limited and plan is expensive...
Like Umobile capped speed but unlimited in 3G/4G is fair enough...

or BUNDLE with Streamyx/Unifi is also MUCH MUCH BETTER than stupid HyppTV...

I'm think TM screwed themselves... the routing and the packages...
Unifi speed also unstable recently since begun TURBOed in early August...

sometime fast and smooth but sometime slower speed or not accessible to selected websites...

Actually T*Mshit got big markets for both Fiber and Mobile, but their teams was TOO STUPID and Managements was TOO LAZY...

Always PROFITS FIRST for THEMSELVES... and NEVER treat customers fair...

20/- get 2 weeks unlimited data at 10mbps not good?

So you want free only satisfied ? 

anyone got this msg from unifi?
RM0.00 unifi: Hey, you're still inactive. Make any usage, reload or purchase add on to remain active or it may be due for termination on 31/01/2019.
I always use the line and even not so, how does it possible that the termination date is 161 days later? they revise the 90 days to 23 weeks?

fxxk this sh1t .. i work in cyberjaya .. just receive my simcard 1 hour ago .. put in my tablet .. speed bloody slow .. lte my foot !