The conversion market is accurate using 3.90 and .66 for last sale on the 27.50 strike for March. Perhaps you're valuing the calls with a higher risk-free rate.
Since C is listed on 6 exchanges and has many mm's at all 6 places making prices I am inclined to go with their prices over your theoretical value calculation.
They're pricing in the 31 ct dividend for 1/31 If you check the "Include Dividends" box at OX, the IV of the calls will be in line with that of the puts.
Everything is below what you believe theoretical value is, not what the market has as theoretical value.
Do you really think that with the single volatility value that you put in or is there as default you are gonna get theoretical values that the market is pricing in!?