Hello,
I have read several posts in this forum about Huawei 3372H and LTE. For me the Huawei is working at map2N and RouterOS 6.38.5.
When I plug in the stick I have to wait a few seconds then LTE interface is available. That is ok.
But I need APN, user and password!
I set these values but when I power off and restart the router these fields are cleared.
Okay, I understand that these values are set implicit by the SIM card. But in Germany there is at least some providers(EPLUS, Medion,…) which define their internet flatrate by APN.
APN = tagesflat.eplus.de ==> daily flat rate for internet
APN = internet.eplus.de ==> monthly flat rate
(FYI: I just need the stick only for a few days during the year on vacation)
So I have to set the APN, username and password
And there is another problem:
I have set my flatrate at the provider website and I set APN in RouterOS. But after restart of map2n the APN inside the RouterOS is cleared and that means that my whole prepaid value is lost in a few minutes because Medion uses the higest price. 
When I look to my settings at the provider website also my flatrate type is cleared.
When I use the stick directly at a notebook everything works fine and the correct flat rate is used. So I think I need a way to store APN, username and password.
Do you have any solution for my problem?
Thank you very much and best regards