how can i change connection string in *.pbit file without open Power BI

I opened pbit (by unzip it) I found files like DataModelSchema (its writen in josn structure) i change in it "connectionString" and save it and get pbit file back zipping it and rename to pbit. When i open the pbit file after modification , i found Power BI still displaying and connect via old connection string as if i haven't modified any thing. Does anyone know what i am missung to change connection string by just change in pbit file ?