Message, "a record with this combination of values already exists", when adding bank info

Summary

Trying to add banking info for spouse--getting error message already exists

Content

Hello: We have recurring billing to spouses in AR; they have different customer accounts and different bill plans, but the ACH will come out of the same bank and account. We are receiving message that a record with banking account and bank already exists. How do we set the spouse's bank up without getting this message? We tried entering the spouse's account under the primary, but when trying to "add" the spouse's banking information (rather than "create"), nothing comes up in the search (even tried adding an "account name" on the primary's bank account), still nothing comes up in the