Closing my account

I am trying to close my phone account but my App keeps requesting to phone me on my 10 digit Canadian phone number which I no longer have access to.  I have attempted to speak to support on chat but the virtual assistant tells me to give them a 10 digit account number.  My account number is [mod edit - private info].  All I want to do is close my phone account and pay the outstanding balance for both phone numbers on the account. Please help me.