Send a text message saying that it is an influx of mainlanders.

According to your information, you should have roamed the border and used it in this city, but because you received the signal from the border roaming place, there are roaming charges in the surrounding cities. At present, China Unicom has basically solved the roaming problem in most areas by various means. However, due to the characteristics of mobile networks, the signals covered by the networks cannot be clearly divided like administrative areas, so this problem cannot be completely avoided from the technical level.

In this case, you can consult your 100 10, and ask the staff to help you verify and handle it.