Galaxy S6 won't recognize my SIM card

I just switched to Android and got a Galaxy S6 brand new from Wireless Providers last week. It worked fine up until today (five days of normal use), when it gave me the error message "No SIM: Insert SIM Card." I've tried all the normal recommendations on this such as cleaning the card with an eraser, soft cloth, cleaning cloth, q-tip, dry sponge, using compressed air to clean out the slot, etc. I also tried restarting the phone with no effect, and a factory reset had no effect either. I would really appreciate some new advice on this; I also plan to head in to an AT&T store here shortly.