You have to purchase a 3rd party service to turn the multi currency feature off in the QBD data file.
If you are dealing with multi currency transaction, you may utilize this 3rd party payment service.
You may release an invoice and get paid in USD, and your customer in CA pays it in their local currency (i.e CAD). You don't need to turn the multi currency feature on. Unfurtunately, it only sync with QBO. You may consider using a 3rd party importer tool if required.