Can I prevent providers from changing settings in their profile?

Yes - go to https://cms-issc.nz/help/supplier/account-review-settings for help with this

You may want to prevent providers from changing:

Their level - level should be 1-6

Their status as ACC ASSIGNED/INTERNAL under Provider ID

Their GST status - if a provider becomes GST registered, you need to know when, in case any payments need to be re-run to take account of this, and also to ensure that the NOT GST REGISTERED tickbox is unticked, as that will override any information in the GST number section.