How to add a sales rep to my contacts page using the lookup function pointing to my interactions tab?

I have a contacts tab with all of my customers and their contact information. I’d like to add a ‘sales rep’ column. The sales rep information is on my second tab, interactions. Every time my sales rep enters an interaction for one of my customers multiple times, their name shows up multiple times on the contacts tab for that customer. I just want the sales reps name to show up once. I’ve attached an image to help illustrate what I’m talking about. Any help would be appreciated.