YOU SAID:

I have worked over 3 years for "Google Express" through "Convergys"

INTO JAPANESE

私は3年以上 "Convergys"を通じて "Google Express"

BACK INTO ENGLISH

I have been using "Google Express" through "Convergys" for over 3 years

INTO JAPANESE

私は3年以上 "Convergys"を通して "Google Express"を使っています

BACK INTO ENGLISH

I am using "Google Express" through "Convergys" for over 3 years