Some users reported that because the signal display on their mobile phone showed no abnormal sign, they only discovered the issue when making a phone call or trying to access the Internet via 3G and 4G.
After trying different actions like removing and then re-inserting their SIM card, or turning off and on the mobile data connection, or even restarting their mobile phone, only a few of these users could reconnect with the network.
However, at 10am on the same day, Viettel was able to fix the issue, and all became normal again.
Explaining the reason of this technical problem, Viettel said that since it updated certain systems for its 4G technology in the evening of September 11, the abnormal situation occurred. This issue, nevertheless, has no connection with the technical preparation for the upcoming mobile phone number changing process.