Also what is the make and model of your phone?
For me, I turn off data when I'm in an area of weak coverage around my house to ensure my cellular data is not used. I turn it back on when I leave the house.
While the data is turned off.... SMS text messages can still reach me as text msgs do not use data.
As with most of my answers on here, because we don't know the account specifics I can offer you all the scenarios that would result in this:
1.) The most likely- You're on a shared plan with one or more subscribers and share data with them. You received a text stating, "TELUS Update: Letting you know you've used $50 of CDN data and are now blocked. To unblock data and accept further data charges, reply YES to this message. Manage your usage and settings at telus.com/my-usage". This doesn't mean that you necessarily texted back yes as you are confused and asking the question. However, when you open your Telus account and put other people on it, you are accepting the charges the other people may incur. The data manager allows you to what your other subscribers can do. The other subscribers are defaulted to having permission to accept charges to data overages through SMS (they also get this text and can text back yes) allowing the whole account to be unblocked. You can change these permissions by logging in to the app or telus.com and removing this or by calling in and having this removed. So another subscriber on your account may have unblocked that block. OR another subscriber may have access to telus.com with their email or know the password to your telus.com login and logged in and unblocked the data on your profile. Those are other common ways the data can be unblocked.
2.) Evacuation order- Are you in BC? In one of the Evacuated areas? Telus has flagged the accounts of evacuees of the BC wildfires and is offering them free overages from July 7-31. Your data may have gotten blocked because you may have incurred overages due to this situation. You should have gotten the free sms stating that you would not be charged for any such overages. However, due to the unexpectedness of such a emergency, there was no time to update our notification system to stop the normal notifications going out to our Evacuees. So while they did get the SMS telling them they would not be charged for overages. They are also getting normal sms saying they are blocked and incurring 90% data overages, $10, etc. They can just ignore all of these until the 31st. Even if you never contacted Telus about this, it's likely that person came onto your account who is checking these accounts to make sure they have access to data right now and just unblocked it for you or ran a system script to make sure you could access up to date information about evacuation orders. They have not communicated how these accounts are being managed internally so I can't say for sure.
3.) Rateplan or billing change as of late? Did you perhaps change your rateplan or a feature this cycle? By calling in to add more data or change your data features, you may have gotten more data. Therefore, the rep would have automatically unblocked your data because you now had replenished your data and didn't need to be blocked anymore. For instance if you added a data top up, or upgraded from 1gb for $25 to 4gb for $45 immediately.
4.) Delayed sms. For some reason in rare instances, the data notifications can be delayed. Like reallyyyy delayed. If they are delayed it should only be by a few hours. Which is why we promote our telus.com desktop site and app. But, we have seen issues where it comes from the previous cycle's bill and just randomly alerts you in the middle of a new cycle. I would check your last bill and see if you got over $50 in data overages on any of your lines. Maybe you had overages last cycle and somebody consented to it and you are getting a delayed sms response now. Super unlikely. That's why I put it as number 4!
In any of these cases, let us know what happens! I'm always curious what the answer was!