Depending on where you live (part of the city), head straight to SBI Nimhans branch.
You don't even need to ask for someone, just stand there for a few mins. The first person you'll be greeted by, will be an SBI credit card agent standing like a guard trying to ask everyone and their dog if they need a credit card.
Most SBI agents in Bangalore aren't really SBI agents. They are generalized and try to share your contacts with other agents in hopes of getting you credit cards of banks you may never require.