I am in Cambodia. What if Unicom card has no signal? Urgent need to receive SMS verification code, urgent, etc

If you use it abroad, you need to turn on the international roaming function to use it normally. Prepaid users do not need to apply. By default, international roaming services in Hong Kong, Macao, Taiwan, Malaysia, South Korea, Vietnam and other regions and countries will be opened. Post-paid users can log in to the online business hall/click "Business Handling" > "International Business" > "International Roaming in Taiwan, Hong Kong and Macao" to open or cancel international roaming rights and choose to order superimposed packages. In some areas, post-paid users need to be online normally and their available ordinary deposits are greater than those in 500 yuan before they can open international and roaming services in Taiwan, Hong Kong and Macao (due to different city policies, the specific preferential policies shall be subject to local policies). It is recommended to contact the local manual customer service to find out.