Nissan Milnerton - Shocking level of Service

I am disgusted in the level of service I have received from the Nissan branch in Milnerton. I have attempted to correct a mistake from their side WRT my service and maintenance plan since January this year. I have spoken to the sales consultant , i was referred to the sales manager then referred again to the finance manager from there to the complaints manager. The last person who promised that this will be sorted was Nadia Lawrence. To date I am still in the same situation I was in January , 3 months ago when I started this process. There has little to no assistance from Nissan WRT calling back even after being promised to be called back within the hour, I am still waiting for this call. I have used my resources to get into contact with them each time. I am now at the point where i am not sure who or where to turn to. Can someone please get back to me ASAP Via Cell ********** 510.