There seems to a be assumption from the non-pilot Brazilians in the forum that an altitude clearance applies to only a segment of a flight. i.e. until Brazilia. I'm not sure that this incorrect assumption has been clearly debunked.
Unless specific qualifiers are added, i.e. "Cross Brazilia at FL370, then descend and maintain FL360.", then an altitude assignment is in force until amended. It is completely normal to have a situation where your altitude assignment is planned, and expected, to change later in the flight. The flight, however, DOES NOT change altitude until told by ATC to do so.
It is also not unusual for non-standard altitude assignments to be used. They are used when factors such as traffic conflicts, aircraft performance limitations or weather conditions prevent using the standard altitude or make using it undesirable (i.e. turbulence). There are also areas of airspace where non-standard altitude assignments are, in fact, standard. The majority of the state of Florida in the US is one such example where they segregate altitudes based on North vs. South instead of East vs. West due to the geography of the state. A pilot who is not familiar with the area will not necessarily be aware of the local differences.
The bottom line is, you don't change altitude until told to do so by ATC.