why does my phone tell me I am roaming when I try to call certain numbers

The best answers to your questions can be provided by your Cellular Service Provider. Please call them and they will be able to explain why roaming appears on your iPhone and how it may or may not affect your current plan with them. Roaming feature should be set to on when you plan to roam outside of your Cellular Service's coverage. It should be set to OFF if you are normally within your Cellular Service's coverage area. In some cases Cellular Service Providers charge extra when roaming.

As I mentioned above, please have a discussion with your service provider and they will give you the right advice that you are looking for.

Axel F.