Ok, it seems the unit is responding, I can set it up, make and receive calls but am unable to get any functional IP traffic.

Current status:

• Unit enabled
• PDP configured (same as reported by a phone)
• LTE connection
• network attached
• network activated
• can configure either LTE,GPRS or WCDMA
• unit reports to have a connection
• can make a call
• can recieve a call

configuration:
+CFUN: 1
+COPS: (2,"T-Mobile NL","T-Mobile NL","20416",7,1),,(0-4),(0-2)
+ZPLMNBAND: 3,20416,3
+CGDCONT: 1,"IPV4V6","smartsites.t-mobile","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0,0,0
+CEREG: 1,1
+CGATT: 1
+CGACT: 1,1
+ZPLMNINFO: "20416","T-Mobile NL","T-Mobile NL",2
+CSQ: 140,99,17

But...
I'm unable to make a network connection. no IPSTART, or CMPING, they all return:

+CME ERROR: 30

Which, as far as I can see, means : "No network service"

What seems illogical is:
+ZPLMNBAND: 3,20416,3

Which would indicate the750mhz band, which is weird, as it should be 900 or 1800
+COPS: (2,"T-Mobile NL","T-Mobile NL","20416",7,1),,(0-4),(0-2)

I must be doing something wrong, but what..
Any suggestions would be greatly appreciated.

@m5stack

Yes, I found and used this example.

Although the code Serial.printf("FUCK STC\n"); on line 305 was not very inspiring, I did get something to work.
The device registers with my provider after setting it to auto and entering the pin, it is getting an ip number and two dns servers but the ping test fails with the message: +CME ERROR: 30 (No network service)
No clue yet to how to fix it.
I did find the 350 page at command reference and am using a combo of the chinese original and a google translated page, but a working sample would definitly help.
The data-only sim works just fine in a phone btw.

Thanks for your response btw ;)

Did you get it to work?
I'm currently working on it, using the example from the documentation. It's still unstable so I have some work to do..