Im being billed twice for repairs not done proprly

i took my car Mazda3 sedan 2008 model, reg XCP244GP for repairs to Mazda garage in Newcastle, the problem was the leaking oil and the vibrating steering ,i was charged R9 508 (including service) this was in July. the problem persisted i informed them and they said i must bring the car back.<br> took the car back to them and it stayed with them for about a week, 5 months later Im still sitting with the same problem. oil still leaks from the car and the steering wheel still vibrating.i called again this time they said i must book the car for the 15th Dec, now they are saying the problem is with the gearbox. Im being charged an extra R7 372.30 for this. That means the problem was not attended properly 1st time. i asked the Lady whom Im dealing with (Bonnie) and sent her an e-mail but Im not getting any answers.Why must I be billed twice for the *********** workmanship done?<br> this is really irritating, surely i cannot be liable for the costs again!!!!