Did you get an order number at the end of the checkout? It may be worth
checking your emails as you need to click on the link which will direct
you to a page where you confirm all the T&C's for the SECCI and device
plan repayment.
You need to get a PAC code from your previous provider. You can do this
by texting PAC to 65075 from the number you want to keep. Once you have
the PAC code, head to o2.co.uk/keepmynumber and fill out the online
form.