Heard a bang from engine it's now growling when.

What have you tried so far? Check the belts first to see if one is broken but if the car won't go into gear, it's likely a transmission problem. You didn't say whether it's an automatic or manual transmission so to cover all the possibilities, the most common cause would be a cracked flex plate for an automatic or a broken shaft or gear in a manual transmission or the clutch disc fell apart. A broken axle shaft is less expensive to repair but you would typically have a horrendous banging and vibration, depending on which joint on which end of the shaft broke. There would also likely be a small puddle of fluid under the front of the car.

If you can't see anything obvious, have the car towed to a mechanic who can visually inspect it.

I'd still head for an inspection. I can't think of anything in the transmission that would make a loud noise, then cause slipping, but if it is slipping, severe damage can be done to the clutch plates in an automatic if they overheat. That might be avoidable if the car isn't driven too far. Hopefully the problem isn't even related to the transmission.