some guy just told me to report someone for swapping lanes with his friend

Yeah, that's... uh... not a bannable offense. Like, at all.

Why did you even open a thread for this? xD What is there to report? ''Omg, riot, these people swapped lanes, permaban them''. Unless they intentionally did it to troll/feed there's nothing to report. That's like people who insult you for kill stealing, even if done on purpose, there's no category for that.

Actually it could be ban able as dumb as that sounds. Riot specifically said that playing a roll other then the one you were selected to play is ban able. If someone on the team wanted to report it could be something.