Originally Posted by bbtrvl

She was not given an upgrade because it is now illegal for banks to increase the annual fee of an account in the first year, even at customer request (due to predatory practices of some banks in the past)

Probably the thing holding up the plus card now is either: an automatic block preventing both accounts existing at the same time, or: Barclays extended the maximum amount of credit on the first account, leaving no available credit to be allocated to the second.

Either way a call to Barclays is in order. Maybe should talk to a credit analyst (someone authorized to approve/reject applications and modify credit line) and not just a front-line customer service rep. Legally they cannot convert but they may be able to approve the new account and cancel the old one at the same time and possibly even allow the plus card sign up bonus.