Tell the ISP you're signing up with that there's no drop for their service, and have them run a new one to the office. Check your local laws about touching their wire or box on the outside of the house before removing it.
Also, it's really easy to patch holes in drywall with a little joint compound and matched paint.
Otherwise, MoCA and powerline ethernet can work. Modern wifi is pretty good too, though consider walls, etc. between points A and B and which frequency you'll be using.