You can exchange your old bike for a Bajaj Pulsar NS 125, but the process and valuation will depend on several factors including the kilometres ridden, physical condition, and number of owners of your current bike. The exchange program may offer immediate financing and other benefits, but the specifics can vary depending on the dealer and any ongoing promotional schemes. It is advisable to contact a Bajaj Auto authorized dealer or check with local distributors for the most accurate and up-to-date information on exchange programs and their terms.