LTE/4G connection quality in São Paulo, Brazil.

Greetings!

I know this is an old topic, but it is related to my problem.

We have been using RBS Mikrotiks with LTE for mobile transportation for a long time. However, lately in my region in SP, Mikrotiks are having difficulty connecting using LTE/4G. However, if I remove the chip and put it in a regular cell phone, it works perfectly.

What could be happening? Has the frequency changed lately? How can I get help?