In case there is duplicate vendor (B) with some spelling mistake, then you can merge vendor (B) into correct vendor (A) by following steps:

1. Change the name of vendor (B) to some other name as vendor (C) in vendor registration and inactivate the vendor (C) to not use in future.

2. Goto Ledger Accounts under Financial Management and merge Ledger Name (B) to Ledger Name (A)

3. This will update all records of vendor (B) to vendor (A).