How do I switch mains when I am used to one agent?

I am trying to switch from Reyna to Raze or Cypher as Reyna is always picked constantly and it gets to the point where people are too toxic picking Reyna, please help me switch agents.

well just play the other agents more often and watch some tutorials for lineups, etc (or highlight videos from raze/cypher mains and try to understand everything they do and why they do it)... That's the best way I guess since you cant be a pro with a new agent without any practice.

For me the best first thing to do is knowing your agent. Learning the agent skills and how to optimize it. YouTube is your bestfriend for it. And then ofcourse, train your new knowledge into battlefield.