I need to change my direct deposit banking account

you can not change your bank a/c in time to get the 2nd stimulus into the new a/c. by the time e-filing for 2020 opens (late January) the deadline for the IRS to issue payments will have passed. the IRS will send to the last dd a/c on file. 

Jan. 15 is the cutoff date in the $900 billion stimulus bill by which time the IRS and US Treasury must stop sending payments. If you don't receive your full second stimulus check money by Jan. 15, you will need to claim all or part of the missing amount when you file your federal tax returns in 2021 through the Recovery Rebate Credit. You'll also be able to claim any money the IRS still owes you from the first round of payments.