To change from bromine to chlorine you need to do a 100% water exchange. The bromine degrades and goes away very slowly. Every time you add chlorine now, it will just reactivate the bromine.
To be honest, we refrain form using the"BBB" moniker anymore as most pools never (or seldom) need the last two "B"'s. Folks heard BBB and ran out and stocked up on Bleach, Borax and Baking Soda, generally unnecessarily. Most pools, once stabilized only need chlorine and muratic acid.
BBB is a old term, bleach baking soda borax, we like TFPC, trouble free pool care, since is more accurately describes the process as many people don't need borax or baking soda.