EDIT: Sorry I replied to the wrong post.

But regarding your data and voice issue, it sounds like your Data is set to LTE only and your phone does not have VoLTE, thus when data is used, a LTE connection is formed but there is no Voice connection.

What phone are you using?

Are you able to enable VoLTE?  Are you able to change your data settings to auto LTE/3G?

Thank you for your reply.
My phone is OPPO A1K.
I couldn’t find any VoLTE enable in my phone settings.

My network settings show “4G/3G/2G (Auto)”, if that what you mean.

Sorry I replied to the wrong post.  Please see my edited response above

Just to give more background:
This issue just happened like 6 days ago (when my data bundle finished before the new billing cycle). Everything used to be fine before that, except for one issue I didn’t care much about. I couldn’t receive multimedia messages before. I always got an error saying “Multimedia message couldn’t be downloaded”. I don’t know if this is relevant, but I didn’t care about it before.

Your need cellular data enabled to download MMS.  Wifi will not work for MMS.

Have you tried restarting your phone?

What phone are you using?

Are you able to enable VoLTE?  Are you able to change your data settings to auto LTE/3G?

Even with mu cellular data, I was never able to download MMS.
And yes, I restarted the phone many times (also tried removing the SIM), and it didn’t fix it.

My phone is Oppo A1K

Here are the frequencies/bands that Koodo primarily uses:

2G: None

3G: 850Mhz (B5), 1900Mhz (B2) - (Both used for 4G in some regions as well)

4G/LTE: 1700/2100Mhz (B4), 700Mhz (B12/13/17/29), 2600Mhz (B7)

5G: 600 MHz n71, 3500 MHz n78, 1700/2100 MHz n66   

And this is what your phone uses 

https://www.gsmarena.com/oppo_a1k-9673.php

2G bands GSM 850 / 900 / 1800 / 1900

3G bands HSDPA 850 / 900 / 2100

4G bands 1, 3, 5, 7, 8, 20, 28, 38, 40, 41

You only have one 3G band and one LTE band that works with Koodo so your coverage is not great to begin with.

Koodo also started to limit VoLTE access to phones on this list. 

https://www.koodomobile.com/help/volte

So if you go to Settings > Connections > Mobile Networks > Network mode (or a similar path for your phone settings), can you switch to 3G only (it may appear as WCDMA or HSPA). 

If you do this, can you use data and call at the same time? 

​@Dennis 
Thank you for your help.
I really tried every possible solution, and nothing solved it.
I ended up getting a new phone !

Regards,

Mohammad

Sorry to hear it had to come to that. But older Chinese phones often missed frequency bands most often used in Canada.