Can you tell at which server and which date/time (UTC if possible or at least specify the time zone) this occurred so that we can check logs?
But let me already warn you that our general stance here is that if an admin tells you something you are supposed to comply. It's a very simple thing and I believe it should be obvious. From your own words here it sounds like that's exactly not what you did. Instead you started to discuss and ask how to file complaints.
Even if you had good reasons for this, during the game while an admin is waiting for you to fix rule breaks he pointed out is
not the right time and place for that.
Unfortunately keeping an admin busy with endless discussions is something that people often think is a viable tactic to get by with a rule break or sometimes just to troll the admin, because they're angry they were reprimanded. So we are very sensitive to these things and tolerance for turning the in-game chat into a discussion forum while the actual rule breaks are still not being worked on is rather low.
Especially rule 3 is a good target for that, as by its nature it always leaves a bit of room for interpretation. Which is exactly why our detailed rules say this:
You can still come to IRC or post on the forums if you think a rule should be changed or if they should cover a specific situation and we can talk it through in an objective discussion. But while in the game, do as the admin asks you to do, even if you don't see it in the rules. Don't argue with an admin during the game on how you understand the rules in a different way – obey the admin instructions first, then join us for a factual discussion later.
Source: https://wiki.x-base.info/OpenTTD/Rules#h511-28