Over 1 month's work - still repairs are not done

How does a car dealership service centre (representing a trusted brand like Toyota) go about repairing a mechanical fault to a 4x4 ... and after 1 month of trying, and in the meantime replacing a bunch of parts, still don't manage to have the fault repaired ? How does this then get escalated and specialists brought in to find the problem and fix it once and for all ? And all this on a R 500,000+ vehicle ... surely, the customer's needs must be strived to be met quickly and effectively ? Even if my confidence in Toyota has been dealt a major blow (this is my 4th Land Cruiser), I still need the car FIXED before I can even try to sell it !! What do I do next ?