I have the same $25 credit showing as $0 issue.
I called and spoke to billing about it. Billing acknowledge the line but claimed the $25 credit could only be used towards a service charge i.e. the $80/month which was free for two months. The order confirmation I received says the $25 is credit towards "your bill" and makes no mention of only being applicable to particular charges.
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The call was escalated to a resolutions department when I said I'd considering getting the TIO involved. Resolutions reiterated the same thing and said the system will not let them apply a $25 credit as the account is closed.
I can't be bothered going to the TIO for $25 and don't want to draw any more attention to my account. I've accepted the 40k points has now cost me $99 instead of $74