Random outbound number when calling a lead on different days

I have been using the dialer for about a year. The system uses using random numbers if you are calling the same lead in 1 day. However, when calling the same lead on different days, the system always uses the SAME outbound number. I would VERY much like to be able to use random numbers each time I call a specific lead, even when calling them on different days. I believe this would help my connection rates because then I can call the same list even daily for a week or two and the person will not see that it's the same number calling them every day until hopefully they answer. Thank-you!