Hi Topdealman,
I work for Vodafone and can shed some light on this.
You'll need to send your 30 written notice to the disconnections address which is:
Vodafone Ltd
Vodafone House
The connection
Newbury
Berkshire
RG14 2FN
If you state on your letter that you'd like to migrate to Pay as You Talk, we'll arrange for this. You need to include your name, mobile number and password/pin number. You’ll also need to make sure the letter is signed.
You'll keep the same mobile number, SIM card, and phone. On the day of migration, you'll probably notice a small amount of no service on your mobile. This is just when the migration is taking place. Simply switch your phone off and leave it for about an hour. Then switch it back on and you should then be on Pay As You Talk.
To register the phones on Pay As You Talk you’ll just need to call 17298 from your phone and to top up, you’ll need to call 2345.