In my phone, it says that the downstream bandwidth of LTE is 10Mhz. But if a carrier frequency of 900Mhz has a bandwidth of 20Mhz, i.e., frequency ranges from 900Mhz to 920Mhz, then I have almost half the BW of my base station. It's impossible. Can you approximately tell me how much BW will I get if there are a 1000 users in vicinity of that base station?
You may have that peak bandwidth available on your particular phone. LTE is very adaptive. When you want a burst of data, you get a burst of data. When you don't, others are using those spectrum resources.
This is an excellent overview of how the system works.
Your signal (on the downlink from base station to your phone) may occupy 10 MHz, but that doesn't mean you have exclusive use of that 10 MHz. It is likely being shared with other phones that are also connecting to the system through the same base station. This sharing is sometimes known as multiplexing or multiple access (although multiple access, strictly speaking, should apply only in the uplink direction from phone to base station). The radio interface technology that LTE uses to accomplish this is OFDMA - Orthogonal Frequency Division Multiple Access.
You can think of it as there being a time-frequency grid of discrete resources, that are allocated to different phones dynamically.