Problem Description
I bought a Greater Bay Area prepaid card from Macau Telecom a few years ago. When I first used it in the mainland, the phone calls, text messages, and Internet access functions were all normal. Later, I suddenly found that I could no longer make calls and text messages normally, and only the Internet function was normal.
Cause Analysis
At first I thought it was because the authorities had restricted the use of overseas phone cards. Later it was found that it was caused by the operator’s system upgrade.
Solution
Turn off the operator VoLTE check and enter *#*#86583#*#* on the phone dialing interface.