The account will be closed automatically once the number port is successful.
Your credit card will not be charged once the account is closed. AutoPay will be terminated.
AutoPay might charge you one more time to renew your prepaid plan if the billing cycle happens while the number port is in progress (before the account is closed).
This would just be bad timing/planning, the payment would be "wasted" on some or all of a billing cycle you won't be able to use (because the plan cycle will eventually be halted when it transfers service to your new provider), but it can't be avoided because your number has to be active to be ported. Your best option in this instance would be to login Self-Serve and "change plan at next renewal" to the cheapest PM plan available, waste as little money as possible.
Mobile number ports can take minutes, hours, or days to transfer. CRTC allows them to take up to 10 business days (or more under certain conditions in certain territories). You can also expect a few business days of incoming/outgoing number mixups or malfunctions before all the nation-wide network machinery is fully updated, especially with calls outside your local calling area, especially if "your" phone number was originally issued to a different number block in a different calling area.
Public Mobile (like every other Canadian wireless operator) does not issue any pro-rated refunds for unused portions of prepaid plans. They also do not refund any funds/balance in account, do not refund unused Add-ons, and do not refund or credit any Rewards which haven't yet been issued.
