I probably would have still told him about the free refill, but I can't honestly fault you with how you handled it. My thinking is: if the guy learned after the fact that refills were free and he was a big enough jerk (which it sounds like he was), then what's to stop him from complaining to the management that he was improperly charged and that I also never told him refills were free?
Sometimes being right isn't enough - even if "I was just following the customer's explicit instructions."
But still wouldn't criticize you for how you handled it.
The manager would have taken my side. I done what he told me. Yes, it was perfectly alright with me to let him have 2 glasses of tea. lol People complained then and complain now about everything. Most people are just looking to get something for free. They could care less that they get someone in trouble. If there is a legit complaint then okay but if you are just cheap and trying to get something for free then stay home if you can't be happy with anything.
I worked a part time job in retail once and these two people came in after parking their motorcycles on the side walk and make a few purchases and as they paid they told me how stupid I was and insulted me for several minutes stressing how STUPID I am. The assistant manager stands in an aisle and listens but does nothing to intervene. These two people pay and leave the store. The manager comes to the register and says "whose bags are these" - I said those belong to those two smart people who just left the building. She said did you not try to stop them? I said NOPE! lol
They were traveling and just passing through. Don't know when they realized they didn't take their stuff. LOL