Orange Pi Zero + 3g modem + wvdial

Hi everybody!

Need some help with understanding of some stuff in my Orange Pi zero.
I have next issue:

        I have Orange pi Zero and Huawei4510 3g usb modem. Orange pi do some 
    measurement and send them on server.
       All this stuff works great.But: 
    my provider have session limitation(3 hours). After 3 hour i lost my orange pi from 
    netework, but i see that 3g modem lighthing as he have connection.When i turn-off 
    modem from usb and plug it again, he lighthing  that he  catch network, but 
    services doesnt sent data.  i'm using wvdial for managing network connection over 
    3g modem. I have script whitch reload wvdial connection. 

I tried :
    - reset wvdial every 1 or 3 hour
    - reset my services
    - service network restart every 1 hour
    - kill ppp0 interface

Made experiment: 
    - i wrote script which writes ping result in file by crone every 10 minutes. after 3 hours he lost network

The only thing that help to reconect devices is reboot.
Is it something wrong with network interfaces or wvdial? Maybe someone can help.  
I will be glad to all the answers.