As it stands currently, for tv service with BellMTS you are allowed one self service programming change online every 24 hours. Keep in mind as services transition from old MTS to Bell that could change.
Cory’s right. Once you signed up for service Bell MTS would encourage you to enroll in MyAccount so you can do channel/package changes online. Then you don’t need to call in and/or worry about the call centre’s hours of operation.