Call me on my mobile

I have asked numerous times for the collection department not to call me on the landline (seeing that i am on the switchboard and my supervisor does not appreciate me taking private calls)1 lady told me they cant cause the system calls the number automatically, other 1 refer it to the manager...I have also write a request via e-mail,but seems to be ignored...I am happy to pick up my cellphone when I am on lunch or after 16h00...