Landing Commercial Clients as a Handyman Without Getting Stuck in Endless Repairs

I've been chasing commercial gigs for a couple years now, mostly doing quick fixes like hanging shelves or patching drywall in office spaces. But every time I land one, the client treats me like their full-time maintenance guy instead of a handyman who upsells bigger jobs like full kitchen remodels or installing partition walls. It's frustrating because I'm out here in Arizona the heat makes everything expand and crack faster, so these office repairs turn into repeat calls that eat up my schedule. I try to push add-ons like LED lighting upgrades or custom shelving during the initial quote, but they always nickel and dime me on the extras. Anyone else dealing with this? How do you set boundaries upfront to avoid becoming their on-call fixer? Saw a thread on r/handyman where someone shared a similar story, but their solution was to just walk away from bad clients.