I've been in a similar position. This is a transactional relationship with hard boundaries and it is good not to look for more in it. The best strategy is to be fast, professional, and to funnel them in a way where they can help themselves. Publishing roadmap and providing community forum for support works for some and others just cannot be helped. Live with that and carry on. No human connection will make them pay ten time the money, so just being responsive and reliable will make you the goto provider for the particular need.

Maybe if your product would get more valuable if you were connecting users together and you were moderator of the community, it would've been different, but it is quite different product to sell.