Personally, I think you are lucky. Most Garmin wearers get promoted to their level of incompetence. You are staying where you can win. My suggestion is to leave your challenge. Press the buttons to exit the challenge. Your spot will remain open for you, but as time goes on, Garmin will fill your spot with other people. After a few hours, you can click again to join a challenge. As long as your last challenge is now full, you will be placed in a new challenge, perhaps one starting the next week. You will be at the level Garmin feels is appropriate until you win. After winning, you will be promoted in a week or two to a higher level. Win that level and again you will be promoted. Have you considered a Garmin Connection Challenge? That is when you invite your connections to compete against you for a day, weekend, or week. If you win, you get 2 Garmin points. If you win a generic Garmin challenge against people chosen by Garmin, you do not get the 2 points. Really, the only purpose of the generic Garmin challenges is to introduce you to other people who you, in turn, can invite to be one of your Connections. I don't invite the Bots, just real people (ie, users who have a photograph, a city, a Garmin rating of 1-5, and who record daily activities).
You have to beat the challenge number of steps by 10,000 or more, for two consecutive weeks, then you should automatically be entered into a challenge with a higher step goal the next week. Doesn’t matter what your position is amongst the other competitors