It might link to a local network if T-Mobile has any partnerships with them (Probably China Mobile). However you'd be better to just buy a local sim and pop it in, that's what the dual-sim feature is for after all.
They're not banned, just not used. China Mobile is GSM so assuming it's a GSM sim you have, it'll probably roam on that network. Otherwise like I said, just grab a sim when you go there, it's super cheap.
They're not banned, just not used. China Mobile is GSM so assuming it's a GSM sim you have, it'll probably roam on that network. Otherwise like I said, just grab a sim when you go there, it's super cheap.