I was browsing my inventory looking for extra prime parts to sell for Baro Ki'Teer and noticed that I was able to somehow purchase more Warframe Slots even though I was at 20/20. On a whim, I decided to buy as many as I could just to see what would happen and I ended up buying 61 of them and spending 1,220 Platinum. There has to be a way to reverse this, right?
Edit: The first reply helped me realize that I purchased Warframe Slots which are different from Loadout Slots which is what I was under the impression that I was purchasing.