Firmware version C10B655SP2 / C10B656

When i execute the following commands: AT+CGMI, AT+CGMM, AT+CGMR, this is the result:

Sending: CGMI - Responce: C!⸮ձ⸮Ltd; www.neul.com/ -
Sending: CGMM - Responce: C!⸮ձ⸮Hi2110 -
Sending: CGMR - Responce: C!U⸮⸮⸮⸮00C10B655SP2 -

I assume this indicate the Fireware being C10 B655 SP2.
I see on the forums that the current firmware is C10B656.
How / where to get the latest version?

(i assume that some of my other problems could be solved by upgrading ;-))