Shop NBC Harrassing, threatening me for THEIR mistake , Internet

I purchased a feather bed topper for about $63.00 on a flex-pay of about $21.00 a month.  The first 2 payments were fine.  On the third payment, around 11/28, someone from ShopNBC called and said my card denied the last payment, but I needed to call out the card number again and make sure they had it correct.  I did and they said they would run it again.  I called my bank, they said no problems with the card it must have been a glitch with ShopNBC. So, on 12/6 a lady calls and says the card had been denied twice and I needed to pay immediately with a check by phone.  I responed with the info from my bank and she needed to run it again.  She stated she would NOT run it again...pay by check or the account would be left as unpaid.  This argument went back and forth for a moment until I had had enough of the threats from the woman and I said " look lady, the card is fine, I just used it a few minutes ago to buy something on HSN, I had no problem, so if you want the $21.00 run my card, if you don't then don't run it.......but by god I better not have anything showing up as unpaid".  My bet is it was some moron on the other end punching in the wrong numbers. I don't think it was very savvy of her to call and make threats when my card was fine, always was....I have been using it every day....no problems.  I have proof that it has not gone a day with out being used and has had NO PROBLEMS.  So, for an error on their side, they don't need to send some screaming lady to call and harrass and threaten me.  I will NEVER shop with ShopNBC again and I will make sure that I post negitive reports about their terrible customer service every chance I get.