The same state-owned Chinese carriers will sell you products in Hong Kong that when used in mainland China let you circumvent the great firewall. https://www.larrysalibra.com/hop-over-the-great-firewall-wit...
The regular crackdowns on VPNs mean that many who live in the region long since stopped using them and switched to a mobile plan or prepaid sim from China Mobile Hong Kong or Hong Kong Unicom that provides a Hong Kong IP address and unfiltered internet while roaming in the mainland.