something wrong with my phone line?

hello friend
i'm use phone line over a years,i use to call my mom every two weeks (in VIET NAM) by call http://www.lunextelecom.com/index.ph...=0&e=0&v=0&p=0 then conected to VIET NAM.The last time i call was november 3 2010,but now i can't make phone call from home no more?
try my cell phone or try my sister home phone both working.Email to customer services they said if i can make call from home to local lunextelecom it work then something wrong with lunextelecom services?but i did make call from my cell phone or from my sister house it work then who services have problem?
this it not first time problem,8 month ago i have same thing happen and support team did something with phone line and it work but now they said nothing wrong with phone line?
so do i need call voipo or lunextelecom?
thank you

Have you been able to resolve this with support?

sorry for later reply.I have to wait see how it go,so far working geart but something was wrong for last 3 days?that is inbound no one can call in?soon i pickup the phone the outbound going death?or just let it ring but can't go to voice mail either?have to wait until monday call in for support?
thank you