The experience of a new player in LOL

I started plying LOL like 3 months ago and had a good impression. I especially liked the teamplay. It wasn't easy getting over bots in co-op and trolls in pvp, but I was hanging on and tried to have a good influence on players. Of course I had matches where I was losing hope but tried to make the team at least lose with dignity and have fun doing teamwork. I had only learned lanes, like the basics of teamplay and didn't understood much of roles like jng, adc and sup. So, a few days ago I was doing a pvp match and got in a team that wanted me to do jng, after I said in champ select that I don't know that. So in the game they take lanes and I start doing what i knew about jng: killing monsters. But i could not kill 1 and get killed. The team doesn't change their mind and want me jng so i continue to try to kill monsters and hopping the team would see I'm not capable of that. But they didn't so they manage to win wile i got killed many times by monsters. After the match end, i get banned 14 days for not helping the team and feeding. I send a ticket and explain the situation i was in and that i didn't think the ban was fair, so they respond me with general talk and that i went against the benefit of my team. I ask them how did i do that by doing what the team asked me to and me not being able to defeat monsters. I also ask if getting killed by monsters helps the enemies directly. So another specialist responds me without answering my questions and says that wile i was new to the position, i gave up and didn't help the teammates. I wonder how did i give up if i kept trying ? I cant help feel that i was punished for inexperience wile i get that my only mistake was listening to the teammates instead of playing on my own, witch wouldn't have been fun for me or the team and anyway the ban being to harsh for just that, also considering i don't have precedents. Thanks for the patience and i would like some comments.