I had the same thing happen to me just now I tried to order a phone and sim it was cancelled due to lack of credit score but I only have a debit card so they called asked further questions but I couldn't understand the guy on the phone because the call was such bad quality afterwards I got an email saying I've just ordered 2 sim cards for £16 each and now I have to wait and see what I am or am not getting.
[MOD EDIT: Post split to create own thread]