If you quickly want to know your SBI account balance or last transaction details, you just need to call these given numbers. You need to keep ready your ATM card number and ATM key.
The numbers are
1800 11 22 11 (Toll free from BSNL/MTNL landlines)
080 – 2659 9990 (other lines)
1800 425 3800 (accessible from landlines and mobile phones)
Remember that only first number are toll free number if you make call from BSNL/MTNL number.
last two number are not toll free, call charge will be as normal mobile call rate.
By calling above number you will not be able to perform many other banking facility like you can do with internet banking.
If you want to use some more activity with your mobile for mobile banking, you need to download banking application for SBI mobile banking into your handset and your need to register your mobile number through ATM. The process of it is given at this link.
You can also check your account balance and mini statement by sending SMS, but first you need to register your mobile number at SBI ATM. Here is the user manual for SMS banking.
The best way is that you get your SBI internet banking activated, use Mobile browser to open onlinesbi.com for all types of banking facilities.