Are you able to shut off imessage to see if texts will work otherwise and thenturn it back on? There’s the following steps to try:

“Reboot iMessage by going to Settings > Messages and turning off iMessage, then turn off your iPhone by pressing and holding the on/off switch, slide to power off, and then wait for your iPhone to start up again. Once you've rebooted, return to Settings > Messages and turn iMessage back on”

If it doesn’t change anything, we can flag a rep to see if there’s anything Koodo-side. 

Hi Goran, thanks for the response. We turned her iMessage off - in a test it sends as iMessage from my phone to her but takes a long time for her to receive (as SMS), if at all. If she responds with iMessage off it doesn’t send until she turns wifi back on. We did a reboot as you suggested and also tried removing the sim and rebooting. She is on the latest ios. Her new data plan, activated yesterday is also not working yet. Cellular data is toggled to on.   

From your description, it seems you got a data block of some type in the account/phone. As you said you already checked your phone, can you check your selfserve » plan and addon to see if a data block was still there. It was common with older plan where a data block was added to avoid additional data charge.

IIRC, there is a setting within iMessage to ‘send as SMS when iMessage not available’. This does need to be enabled on the sender's end, otherwise the message will not fall back to SMS.

Dinh, thanks for the suggestion, the data block was there, so ironically I was paying an extra 5$ to have her data blocked (as part of allowing text images). I removed the add on but unfortunately still no data so looks like a physical trip down to the koodoo store is in order. 

Have you tried to restart the phone (and reset network settings of it) to see if it can help? I wonder if there was an issue with the setting in the phone itself

I just reset the network settings and it is now working - thank-you Dinh!