Firstly, thanks to the posters above who highligthed about 8RMB plans, very useful and I have not seen this info elsewhere.

I got my China Mobile SIM last summer in Shenzhen on a TWOV sticker and paid 100RMB, which included the first month, but if you leave the country and dont keep paying 100RMB a month, the line gets totally disconnected untill you pay again, so you don't receive even messages anymore (important for wechat/alipay and Chinese airlines).

Having read this thread I wrote in the China Mobile app chat asking them to do change it and operator said they will call me back to confirm. Was a bit scared about that as my mandarin is pretty bad (I speak more or less, but I have difficulties with understanding especially when it comes to this sort of specific stuff and when they dont see my non chinese face and dont speak a bit more slowly). What I then did was I went to one of the stores in Hangzhou and they were very nice about it and called the call centre on my behalf and confirmed the change.

From what I understood, it will take effect next month and I will still be able to buy data packages when nessesary.