I purchased a Samsung S9 as part of a Buy one get one Free promotion and have been getting charged for the 2nd phone. Why am I being charged?
Did you verify you qualified for the promotion? Particularly did you add a new line of service for one of the phones?
To qualify for a BOGO you need a new line of service and wait 2 - 3 bill cycles. If you haven't received credits by then, you either didn't qualify or will have to call CS to have a form submitted to fix.