You don't mention what version of CRM you are using, so I will assume 2013/2015.
If you go to Settings -> Customization -> Customize Entities, select Entities and then the Contact entity, you should see a check box for 'Allow Quick Create'. Uncheck the box if you want to disable quick create.
After that, if you only have one active form type of Main available for use, that's the one all the users will see.
Don't forget to Publish your changes after you make them.
Hope this helps!