Downgrade icloud

If you already tried (to no avail) all the steps provided in this support article:--> Downgrade or cancel your iCloud+ plan, I suggest that you contact Apple support directly, using this link:--> Contact Apple for support and service

Regards

Giulio

You can downgrade your iCloud Plan here:

Settings → Apple ID → iCloud → Manage Subscription → Downgrade Options

Select 5GB Free and tap OK. When your current Plan expires, you will be downgraded to 5GB and you will not be charged any more. If you want to downgrade to another iCloud+ Plan, you can do that there too.

You can find more useful information here:

Downgrade or cancel your iCloud+ plan - Apple Support