OK, I begin to understand.
“https://www.ibtimes.sg/china-hiding-covid-19-death-toll-21-million-cell-phones-disappeared-why-41580
“The comparison showed that the number of cell phone users decreased from 1.600957 billion to 1.579927 billion,”
Later on the article states:
“While the drop in these numbers showed a dramatic scenario in China, Tang said, “It’s possible that some migrant workers had two cell phone numbers before. One is from their hometown, and the other is from the city they work in. In February, they might close the number in the city they work in because they couldn’t go there.”
But the whole population of China is just above 1,4 billion
https://www.worldometers.info/world-population/china-population/
Given that the figure will include infants and young children, it means that the average Chinese probably has more than one mobile phone accounts and that maybe some who did have more than one decided to save by abandoning their subscription?