Dealing with a nightmare client on a 240V dryer install today

started the day with a service call for a new 240V outlet on a whirlpool dryer, figured it'd be a quick 14/2 romex run through the attic. customer kept changing her mind mid-job, first wanted it lowset then high, now complaining about the $450 flat rate even though i explained the nec 210.21 requirements. been in the chicago area my whole career and this is peak difficult client bs, had to bite my tongue to not tell her off. by noon im sweating through old insulation, shes hovering asking if milwaukee drill bits are code approved lol. wrapped it by 3 but shes already texting about a discount. tips for handling these types without losing your cool? saw a similar rant in electricians network facebook group last week. watched that electrican u video on customer communication too, but damn.