sim roaming aggressivity not configurable

Hi, i changed my sim operator (Tim) to a virtual operator (Fastweb) and i see often the phone goes in roaming.
Nothing strange in certain areas, except the roaming is during until for half hour in territory i'm sure the roaming is not justified. For trying to force a change i have to activate the airplane mode and then deactivate it.
I tested the same sim on another smartphone with a different O.S. and the problem is very lesser.

Bq e5Hd with Ubuntu Touch ota13,flashed for rc-channel. Actual latest update r469