I tried this on two occasions and they cancelled my internet, home phone and cable tv 2 weeks early. When I asked why it was cancelled early they told me the Bell requested it. I told them that's impossible because I don't have a contract with Bell and they kept stating it was requested by Bell. In the end they didn't care and reactivated my package but wouldn't budget on a better deal. In the end, it took about 10 hours of conversations over 6 attempts and I gave up and agreed to a bad package.
When I'm asked for cancellation for a future date, it's always gone bad as they've cancelled early and I got no call back.