transmission stuck in a gear?? warning light on 90% of time

What is your question?

when the light goes on it appears that the transmission wont shift and that it is stuck in a higher gear. i can take it up to 100km or so still but doesnt appear any shifting is going on to get there. when light is off- it all seems normal. i just had a tranny filter change and the guys never noticed anything at the time but its def got an issue.