my iphone change cellular data without permission

janevanessa94, 

We appreciate you taking the time to update. Another setting to check is in Settings > Cellular/Mobile, scroll all the way to the bottom and see if Wi-Fi Assist is enabled. If it is, turn it off. That feature uses cellular data when Wi-Fi connectivity isn't good. Here's some information on that feature About Wi-Fi Assist.

Thanks.

Good day to you janevanessa94, 

We understand that you’re noticing the cellular data option changing on your iPhone, though you have disabled ‘Allow Cellular Data Switching’ in Settings > Cellular > Cellular Data. 

Can you tell us a bit more about when this happens? For example, when you’re on a phone call or does it seem to be kicking in when cellular data is unavailable on your default line? 

If you haven’t already, be sure to restart your iPhone Restart your iPhone and also double verify that we’re working with the latest iOS version, 14.7.1. You can check in Settings > General > Software Update. 

Thank you.