Ants in the soil may be there for different reasons. They may actually live there but more likely (in my experience) they are there for either food or water. Food coming from root mealies or some other insect they farm in there, water coming from regular irrigation (depending on how dry it is outside where you live). They aren't actually feeding on your plant (most likely) but their presence may be alerting you to the presence of something that is. Was there/is there a trail leading from the pot away to somewhere else?
Ants can be pretty effectively removed by drowning (submerge the whole pot in water, wiggle it around to get the air bubbles out, and wait an hour) but they can also come right back as soon as there's air in the soil again, so that can be a temporary measure. If you identify problem insects in there, they can usually be treated by drenching the soil with soapy water. Like watering to completion, then waiting a few minutes and watering again, then repeating. I use Safer brand insecticidal soap, which I can buy in a concentrate, but I think you can make your own from mild dish soap at 1-2% in water. Then the next time you water, a week or two later (whatever), use regular water and you will start to flush the soap from the soil. It should not hurt the plant if it's at a low concentration and temps are not in the danger zone. You can also treat with a systemic (eg. drench the soil with imidacloprid) but I like to start with soap before I bring out the big guns.
