Problem when used LTE network on Samsung Galaxy A3 2016

[AC Question]

I use Samsung Galaxy A3 2016.
I have problem with LTE network connection.
When I have connected with LTE network often "rate drop connection" although
the network notification showed still connected.
And sometimes the network restarted immediately.
I have used 3 different mobile provider but have same problem.

Change to Airplane Mode just fixed problem temporary.

Can anyone solved my problem?
Thank you.