[Q] German i9300 with China Telecom

Hello together,

I have a S3 from German Telekom. It's unlocked and not yet rooted.

Now I am in China and bought a Prepaid Card with 5GB of Traffic from China Telecom.

It connects to the network, coverage is very well, but only Edge.
When I select "Only WCDMA", it shows full coverage, but doesn't connect. I can't even start a call.

I found out, that non-China Telecom phones cannot connect to the network (only 2G).
Also China Telecom phones may not connect to other networks.

So now I guess if i root my phone, and install a china telecom baseband, it will work? Or does it have a different radio?

I'd really be happy to get answers. I can buy a card from china unicom, it's not a matter of the money. But it's the technical fun :)

Thanks in advance,
David.