[AC Question]

hi
i bought a used note 3 a while ago.i am in the uk but i was unaware it was a malaysian model.it worked fine for a month or so then i got the no service message.i have been through checkmend and various other imei checking sites and it has shown up clear on all of them.my local phone shops do not have a clue why it wont work.im hoping someone may be able to shed some light on the problem? thanks.