Luckily, with mercury.ai bots you will no longer depend on a certain order of a conversation. While this is usually done based on a tree structure of conversations, users that interact with mercury.ai conversational agents can write about everything they want at every point of a conversation.
If you still want to "guide" your users through conversations, you can add quick reply buttons (also known as call-to-action buttons) to your messages. Those can be used as nudges towards a certain direction of the conversation and are a really powerful way to guide users through your bot the way you want it. However, call-to-actions are never the only option of the way a conversation proceeds. This is really great because your user will have the opportunity to have more natural conversations with the bot.
In other words: not having this option is a feature!