I Know this is digging up an old thread, but it come up during a Google search after looking myself, after getting the same declined message. I didn't see any helpful response on any related threads and wanted to offer advice for someone else who mysteriously comes across this decline reason.
In case anyone else sees the same, it is not about your credit score in any way. For obvious reasons o2 won't discuss the specifics as its all internal for their own protection, but generally the things they check for are:
-Do you have too many active lines on one account?
-Have you opened more than X lines/accounts with o2 in less than X Months?
-Have there been lots of orders made and returned/cancelled?
-Have you had your account closed down for fraud, or other misuse that goes against your agreement?
-Is there another order currently pending?
-Have you just upgraded another line on the account in the last X days?
These are not o2 specific things, but things that I know about with other similar companies. I can make a good educated guess and say that my reason for refusal ties in with the second point above. I had 2 lines open, applied for a third, declined for business policies. After having the account 6 months it let me open another. Tried for a fourth, declined for business policies. After having the account for 9 months it let me get the fourth too.
