I just renewed my plan, and I got a text saying I used 75% of my data.
It could be an erroneous message. Log into self service and look at My Data & Add-Ons and have a look at your data. Remember, renewal is in Eastern Time so if you are out west, renewal is happening right now.
It is possible that the counter did not reset properly. In that case you would need to open a ticket to talk to the moderators. https://widget.telus.tiia.ai/publicmobile/publicmobile.html
That's probably an erroneous message. Those data text notifications can be hit or miss - especially when added data is applied mid-cycle.
I would recommend using your phone's data tracker to measure your data use.
In order to be able to rely upon it, you should select the option to 'reset counter', which you should do the morning after your account renews.
This way, you can view the data usage on your device. It should provide the same measurement as what's showing on your self-serve landing page.