Ability to add services to a listing made under the "Listings" tab.

I wish there was an easy way to add services to existing listings. I never knew that you had to log-in to the agent’s account from the admin portal to place an order. Twice now, I have created listings for agents under the “Listings” tab because they just texted me instead of ordering on my site. But, I can’t charge them unless it’s through a custom fee which is quite frustrating.