Speed links

Good afternoon people.
I’m having trouble in a following scenario:
I have a new client that uses the Mikrotik with two internet connected on the device. (EMBRATEL [4MB] AND NET [60B]),
and overnight the navegaço was limited to 2MB for both links. But to do some download the file comes
6 mb which is performed by the link of NET. It is only changed to navigation. I checked everything was tutorials
on the internet and I did not find what is interfering.