i am working in china, i have z-visa,my visa was gonna expired in start of january

so my employeer extend my visa for 6 more months,, now i am in my country on winter holidays, i have my round trip ticket, here some travel agencies were telling me that i should have to get stamp from immigration department again called as (protector). well my employeer is same , i am working for the same company that sponsored me in the beginning.. so i want to know is it true or not,, please guide me , thanks