RE: LHS no longer takes my phone order unless I pay up front
That's likely it right there. If you've never worked retail you simply don't realize how many goofballs will order items that no one else will want, then go get them someplace else. Yes, you've been a customer for a long time, but that doesn't make you special. Everybody who calls that store thinks the same thing- "But it's me! You know I'm good for it!." The store probably has a $400 kit sitting on the shelf right now that some longtime customer had him order that he'll never be able to sell.