I have known Numrich Arms / Gun Parts from the 1960s on as Numrich Arms, then as Gun Parts Corp, and mostly find it now as Numrich Gun Parts. Their print catalog is worth keeping as a reference: my copy is #27 1240 pages out-of-date but with some rare or oddball gun breakdown illustrations and parts lists.
I have ordered from them recently (2008 to last year) over the internet using Visa debit card thru local credit union:
_ rebuilt parts for a Thompson magazine,
_ a magazine body for a display dummy Sten gun,
_ a stock for an M1944 Mosin,
_ cleaning rod for M1944 Mosin,
_ Colt 1911 extractor,
_ two piston shock absorber rings for a Mossberg M1000 shotgun,
_ cloth bags with shoulder strap for M60 MG 100rd belts (perfect size for 25rd box of 12ga)
and decades before that I did numerous transactions snail mail with money orders from the 1960s onward.
I have had no problems dealing with Numrich Arms, Gun Parts Corp., or Numrich Gun Parts. When making paper orders, I did make sure I had the make, model, and their part number correct and double checked before placing the order. At least once I sent a paper and pencil rubbing of my broken part to verify what they had in stock was what I needed. I don't expect their hired help to be psychic. I have not had any billing problems in my dealings with Numrich in any of its incarnations on their end. I may have been lucky since the 1960s and missed years when they were mismanaged or poorly staffed. Their internet order system has always worked for me.
As for the Opening Post problem of pending or charge not showing up, I have had problems with either Visa or the credit union taking days for other vendor charges to show up on my account even though the vendor had been paid. Also I had one pending order with another vendor (Winegers) show pending (-$39.95) until the order shipped, then both pending (-$39.95) and debited (-$39.95) for -$79.90 to my balance, then a day or so later just debited -$39.95. I adopted a policy of keeping a cushion balance for such temporary glitches before placing orders, but I can't recall it re-occurring. I'd blame sunspots.