I created the community billing support channel last year working with Mod Tron and a few Billing JMods. Most of my videos are on OfficialJagexSupport's Community Help playlist.
I think billing support is an interesting subject because solving billing questions often requires some creative thinking. For example, if your card isn't working, have you thought about buying membership through Amazon instead? I had been posting in the billing support forums as far back as 2008, and was sad to see them closed last year.
RSCommunityBilling a small channel, but I'm looking to make it more prominent with new billing videos (such as a new series on microtransactions that I released about a week ago) and possibly some non-billing videos. For example, I could make fairly detailed videos about merchanting or account help as well.
I will definitely check out and subscribe to all of your channels.