Modulation and allocation in GSM900 I want to do one project and I just want to make sure that I've understood correctly.

Human's voice frequency is around 85-255Hz. 

When we talk on phone, carrier is modulated with voice signal in order to shift frequency spectrum to higher frequency for transmission. If we take for example GSM900 which is 876 - 915 MHz paired with 921 - 960 MHz. That means that our speech will be in this GSM900 range after modulation? 

Moreover, how much bandwidth user gets in 876 - 915 MHz paired with 921 - 960 MHz range? Any articles about that?
GSM since it's first day has been digital (Fat32 is incorrect). That means you can't send analog audio. Luckily, analog audio had already been phased out in the 80s, in telecom.

In digital telephony, audio was digitally sampled at 8 kHz, 8 bits per sample, for a 64 kbit/s signal. If you has an ISDN phone, you got this quality at home, but it certainly was used inside and between the central phone switches.

GSM built on that 64 kbit/s idea, but used audio compression. The first codec used was GSM Full Rate, which achieved 5x compression for a 13 kbit/s net data stream.

GSM furthermore divides every frequency band into 8 slots, which means that phones can only transmit short 5 ms bursts and then have to wait for 7 other bursts from other phone users. Band spacing is a mere 200 kHz; a typical carrier gets 5Mhz blocks of spectrum which means 25 bands and 200 slots total.