If you want to cancel your service at any time, just raise this request via your portal account to Billing.
We usually require 30 days notice to do this so any services that are already due at the time of the request would need to be paid in full. This would be within the 30 day period as our invoicing terms are 7 days.
Once your account is cancelled any numbers assigned to your account will be quarantined and will not be re-issued to another account for at least 6 months. Any call traffic to those numbers will get a out of service message
For post-pay customers, this would include any balance that you have on your account and for pre-pay, any balance that you may have accrued for services not covered by any credit such as on the monthly service deduction on the 1st of the month.
Pre-pay customers will need to use any credit that remains on their account as this is cannot be used in any way and is lost once cancelled.