Field Amount of an Oportunity does not hide completelly

Field Amount of an Oportunity does not hide completelly

Hi all, 

I want that fields relative to $$$ from oportunities (Amount and Estimated Incoming) become not visible to my employees. So I went to PERMISIONS, profile--> Employees, module--> Oportunities and make those fields hidden. 

All seems to be OK since I go (logged as employee) to an oportunity and I don't see those fields. 

But if I scoll down and reach to "Historical Phases" (or however it's named.. i'm in a spanish interface) I CAN SEE ALL HISTORICAL STATUS CHANGES WITH AMOUNTS. So it becomes useless all configuration and effort. 

I think it's an error. Or I'm doing something wrong.

Thank you all !!