Carefully read the notifications sent by the cellphone company. When in doubt, click no or shut the pop-up.
Tell your kids to always use WIFI as a free option.
Consider setting up your kids with a pay-as-you-go/pre-paid plan that gives them a set amount of data per month. Once that level is reached, data is shut off.
Ask your cell provider to completely block all data at the Network level. With Rogers or Bell, blocking data at the network level means that no one on the account, including the parent/account holder, will be able to access data. Telus offers a $2/month option which blocks data but allows picture and video messaging.
Outsmart your kid's smartphone. Here's how you do it on an Android device: go into your settings, click on "set mobile data limit," punch in the dates of your billing cycle and tell the phone when to shut off mobile data. Then, go into the Kid's Mode app and follow the steps to lock your kid out of the settings on his/her phone. Your kid won't be able to turn the data back on, but will be able to use WIFI. iPhones offer a similar option via Guided Access in Settings.
If you have a complaint, check your usage and research your account online. You will need this information in order to pursue your complaint.
Complain first to your cellphone provider. Provide your account number and be specific.
If you believe your complaint has not been resolved properly by your cellphone provider, then you can submit a complaint to the CCTS. You’ll find the CCTS guide to Making a Complaint here. And here’s a tip: the CCTS likes online complaints and lots of documentation.