It's possible that on the credit card company's end something is wrong with their metering, maybe insufficient postage and that's why it's being sent back. Then there's the possibility that a USPS worker chose the wrong scan type. It could have arrived at a sorting hub and instead of scanning it in, they scanned it as returned to sender. Since it's just this particular bill I'm thinking it's on the company's end. I'll see what happens.

Cathy