I'm extremely confused. I have two United charges on my credit card, one for $548, one for $391. The $548 charge is fine, it was for a FAR-CLT-DFW-FAR itinerary in June. The $391 charge is perplexing to say the very least. I booked a ticket using a VDB voucher worth $400 for a trip from FAR-DFW-FAR, which was the same price as the $391 charge on my credit card. I've called UA with my FAR-DFW-FAR confirmation number and they've said that there is absolutely nothing showing up in terms of a credit card for that flight and the voucher was used for payment. Any ideas on why my credit card was charged for the flight?