I had to go through similar nonsense recently. I was getting pizza and the cashier said (smiling) "it's better with tip". The first time he did it I figured I'd tip him. He handed me the pizza when it was ready and that was that. The second time I didn't tip him and he was like, No tip?? I said yeah I don't understand why - isn't tip for service? He said well yeah, I'm trying to provide service. As I was about to reply "but that's already in..." he interjected "when you don't pay a tip, I just give you the pizza. But when you tip, I put in a little something
extra." I was confused and just looked blankly and said I didn't ask for anything extra. He stopped arguing and when the pizza was ready, didn't say anything until I was about to inquire. Then he gave it to me - another pizza exactly like the one he'd given with the tip before.
I honestly kind of felt bad, in that he probably wasn't making that much money, and the tip probably meant more to him than it meant to me. But demanding a tip and falsely telling me I'm getting more than I'm paying for is not the right way to fix that, and the pizza wasn't particularly cheap either...