You call chat scripts by using the connect option. You can use connect "chat ..." in any PPP configuration file or on the command line.
Chat scripts are not executable, but the program that is invoked by connect must be executable. You might use the chat utility as the program to be invoked by connect. In this instance, if you store the chat script in an external file through the –f option, then your chat script file is not executable.
The chat program that is described in chat(1m) executes the actual chat script. The pppd daemon invokes the chat program whenever pppd encounters the connect "chat ..." option.