Maintaining a mainland phone number for once a year visits to Beijing?

I go to Beijing every august for about three weeks. I usually buy a mainland chinese sim card from a seller on amazon and they activate it with my passport. This has worked fine but it is a bit annoying because I have a new phone number every time I go and I have to recreate my (many!) accounts that require mainland china phone number verification. Is it possible/does it make sense to get a cheap post-paid cell plan so I can keep the same phone number? Any advice about how to go about this and/or how much it might cost? I have a tourist visa and stay at a hotel. My Chinese is OK but not great—I get lost when things are technical and I don’t have the right vocabulary. I saw that some people were previously able to do this through Three HK for about $3/mo but they now require a HK residency card. Thanks!