020 is the area code of Guangzhou. In the past, the fixed line was basically a telecom operation, and the first number was basically 8. Later, China Mobile and China Unicom all had fixed line services, so the first number was not enough, so the first 2, 3 and 6 numbers were added, which should correspond to different operators. Personally speaking, 6 stands for Tietong, which is the later mobile fixed line, 3 and 8 belong to telecom, and the beginning of 2 may be ChianUnicom.