Thank you very much for replying to this matter.
If I get you right, this is distinctively a problem with modem, whereas the version of the modem included in general update to Kit-Kat version for users worldwide that Chinese developers Lenovo published is not compatible to work with all countries cellular network providers, particularly in my country - Ukraine and the only solution for fixing the problem is to find a compatible/proper firmware of the modem.
Since, my Lenovo P780 is fixed to stock version and never been rooted before, can you please advise if root is compulsory and provide the link with step-by step guide in order to root the phone if it is compulsory to change the modem version and the link with modem versions.
Also, please advise if I will need to change for a custom rom in case of modem change etc.
Thanks again for your kind support,
Originally Posted by stympy
Look in post How about some modems in the section Vibe.
Root your phone and try change modems from there. Backup first.