post https://api-sandbox.bill.com/api/v2/ConnectLargeBillerAsVendor.json
Connect a verified national vendor as your vendor.
When the connection is successful, the verified national vendor information is linked to your created vendor and you can pay the vendor (with /PayBills.json).
In your /ConnectLargeBillerAsVendor.json request, set largeBillerId as the id (retrieved with /LargeBillerSearch.json) that matches your vendor billing statement zip code.