From this link

It reads:

You have 30 days to give your PAC to your new network provider, otherwise your account will stay open with us and you’ll be billed as usual. Here’s how to request a PAC or STAC:

• Via Text.

Using your iD Mobile SIM, text PAC & your Date of Birth (DDMMYY) to 65075 or STAC & your Date of Birth (DDMMYY) to 75075

• In the iD Mobile app or My Account Online.

To disconnect in the iD Mobile app or My Account Online, you can:

1. Open the iD Mobile app or log-in to My Account Online.
2. Tap ‘Plan’.
3. Tap ‘Leave iD’.
4. Tap ‘Get PAC code’ or ‘Get STAC code’.
5. Tap ‘Yes, proceed’.

• Live Chat.

The quickest way to get a PAC or STAC is via text or in the iD Mobile app, but if you’re experiencing issues, simply chat to us.

HTH