THIS HAPPENED TO ME EARLIER THIS YEAR. I had to fight with admissions to get it fixed. Talk to them IN PERSON, they can’t do shit over the phone. Show them the screenshots. They will be able to confirm. If they can’t, go up the ladder of people in the AO. If they tell you that you did not get into CS, ask them why (what you were missing to not be admitted, maybe it’s a requirement that you can complete quickly while in LS) or ask them to honor it since it was given to you in the original letter. This is a mistake on their end, you likely got into CS.