Rule of thumb--when you have a problem that you (the customer) know you have been logical, considerate and patiently waiting for a resolution and still don't have a reasonable response--move higher in the chain of command--get to someone you have not spoken to before. You have been all the above, lay out a timeline of what has happened and who you talked to each time and go higher. Hopefully, you appeal to them in written form. If you can get that timeline to someone that shouldn't have to deal with it they will (S**t rolls downhill) jump someones behind and usually quickly get it resolved to at least your satisfaction. If not to your satisfaction you will have their final answer to accept or call your lawyer. If you feel you have not exhausted your case with BMW NA I would still do the timeline and copy someone up the ladder.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas