In pokemon silver why can't I battle anyone in the fourth gym?

Every time I go in the gym and walk like 5 or 6 steps it sends me back to the posts in the gym why iss it doing tht I've pretty much done every thing!! Peolpe help me and I've only battled the first trainer and it won't let me go any farther...annnddd while I'm at it wat do u think is the best eevee evolution