Contact your directors (if that's not you) and ask them to take it up with the agent. Let them know of your wishes to change landscaper. Your directors are the ones who will make most of the decisions for your complex.
As to getting information from the agent, call them up, email again. It's time consuming but they are acting as your agent.
The protocol is slightly different depending on whether you are a director or an owner. You should have been given a copy of the budget before any service charges were requested for the year in question.