i want to downgrade my icloud storage to free

I had same problem as many others too. I called Apple and here's the answer. If you were successful the first time you tried but it does not show the change, it's because you are paid through the monthly period so it won't show the downgrade. Once the monthly period is over it should show the downgrade. I'll try in 30 days and see if it's correct but it does make sense. I wish they would insert a few words saying this.

If you cancel your plan or you don't renew it, you'll automatically go back to 5GB of free storage.

On your iPhone, iPad, or iPod touch

1. Go to Settings > [your name] > iCloud > iCloud Storage. If you're using iOS 10.2 or earlier, go to Settings > iCloud > Storage.
2. Tap Change Storage Plan.
3. Tap Downgrade Options and enter your Apple ID password.
4. Choose a different plan.
5. Tap Done.

Contact iCloud Support. You may have to try twice.

iCloud Support

Read here: iCloud storage upgrades and downgrades - Apple Support

Contact Apple Support

https://getsupport.apple.com/GetproductgroupList.action