I’ve been playing for a few weeks, but can’t see how to change my defense team.
You need to look through arena to your team. Then clicl on the bold letters that say “defense” it should be where you normal press “fight” then it will take you a place where you can alter you hero lvl.
Ok and what if that is not there?
Then something is wrong, take a screenshot and raise it with support.
Unless you have changed your defense team in the last 24 hours, then you will see a countdown timer showing when you will be able to change it again.
Hi I’m having the same issue. There’s no Defense option.
Hi @Sprankles, welcome to the forums!
If you go to the arena you will see your defense lineup as it is. To the right of it there will be a big green button that says “defense” in it. Press that and you can change your team. You can only do this once every 24 hours, if you have done it already there will be a countdown timer where the green button was.
Hi! Thanks for the clarification! I didn’t realize I had changed it in the last 24 hours. Thanks!!! 
No problem at all. Good to have a nice easy fix for a change.
I haven’t changed my defense im a couple of days, though I keep getting a message saying they split my arena line up. It doesn’t give me the option to deny that split either. I haven’t seen the defense button but once… Could it be that the split is using my 1 change per 24 hours?
The message you got said that your arena had split. Not your lineup.
There were too many people in your arena so they split it into two separate ones. It makes it easier to get promoted.