Switching from Three but PAC code is in use

[finscrim]

I am trying to switch from Three to Vodafone.

I purchased a new phone and signed up for a Vodafone SIM. I've put the new SIM in the new phone, and have requested a PAC code from Three (my previous provider) on my old phone and tried to transfer my number via the Vodafone service: https://myaccount.vodafone.co.uk/settings/keep-my-number/pac

However I receive the error "Sorry, the code you entered is already in use. To get a new code, please contact your old network provider." 

I am having no luck finding an option through Three to request a new PAC code, and I do not understand how it could possibly have been used considering I requested and received it 2 days ago and have not tried to use it until now. 

[finscrim]

I would also like to note that I have tried to sign up for the MyVodafone app to see if there's any options there but receive the error ref '1w0' after entering my phone number.

[AnnS]

I am sure the reason for your problems @finscrim is due to the account not yet on Vodafone systems.  If you have not made a connection to the network to activate the SIM give this a try. Before submitting the PAC again clearing the PC cookies may help.  There is further information for you here: What happens on the day my number moves to Vodafone? 

Numbers do not port over a weekend, by tomorrow the account will be on the network, the SIM should  be active on the network and the keep my number form will accept the PAC.  Although the account should change when the port is completed to show the ported over number, you may wish to wait until this is completed before setting up the account.

Further information here: Getting Started