@yangster your friend has said correctly. You need to work in a company atleast 1 year before changing the visa (or) your current sponsore can give you Arraa- which means after completing 6 months in the company you can take arraa (document signed by your current sponsor and join & work in another company. After total 1 year then you can change your visa to that new company.

This thing is a default and will not be mentioned in any company contract. Hope this helps you.