Depends on what time you check your usage. Any time after midnight EST and up to 7am next day is usually their maintenance period and no one can view their usage data. Are you using the mobile app or the website?
Indeed, there may be some delay with the data usage information due to a system maintenance. However, a delay of several days is not normal. We will need to access your account to make the appropriate verifications. Since we can't disclose any information about your account here, we recommend to contact our technical support at: < http://www.videotron.com/residential/contact-us >.
We also sent you a private message, you can reply to it and leave us your contact information. We will make sure one of our agents calls you back to verify this further. Thank you!