Sdruvss, what you say , or at least what I understand from your previous post, is not correct.
This might be due to , as you say, you "English lack of proficiency." but
Let me correct a few points, from a European ATC view of course .
FL370 is a normal RVSM level. Under radar controlled airspace , it is up to ATC to assign FLs , regardless of Flight Plan REQUESTED FLs , and of Level allocation scheme ( direction )
Again , under positive radar control, ATC overrides Flight Plan.
Changing headings without clearance is not authorized, ATC always clear an aircraft to fly A to B either via heading, track , point to go, etc.. or via Flight plan route. Therefore the turns that subsequently follow along the cleared route are authorized. In the vertical plane, the last FL cleared is the one to follow, regardless of Requested FLs , UNLESS IN RADIO FAILURE.
In radio failure a relatively new ICAO procedure applies ( see among the first pages of this thread for the details, no time to check for you ) in which after a certain time the pilot in command should disregard previous clearances and follow strictly the filed flight plan.
Now the big discussion and heavy debate we had a year ago, is : were they in radio failure , and if yes , which procedure did they follow, or were they intending to follow ? There was apparently a large discrepancy between the USA FAA "NORDO procedures" and the ICAO recommended ones. Which ones Brazil had published in their AIP at the time of the accident would be interesting to have. We had no reply on that question. But I am sure CENIPA , will look into this.
Your invented " ideal" R/T exchange that should have taken place makes no sense to me at all.
Finally , back to a previous post of yours : while lecturing Prof Ladkin, you said that the Brazilian RVSM bible ,called NABR-2, is only in Portuguese. I doubt this very much.
If , as i suspect, NABR-2 is only a translation of the ICAO RVSM introduction book, then RVSM as no bearing whatsoever in this accident.