I have a new client and need to invoice them and record their payments in a foreign currency. On the FAQs and forums, it's written that I just need to select the appropriate currency when adding them as a new customer. 

However, the software does not allow me to do this. The currency when I create new customers is stuck on my base currency, and cannot be edited.

What am I missing ? 

FYI - I am on the free plan, but thought that the free plan allowed for multiple currrencies (see for example Bank Details in Invoice | FAQ | Zoho Books )

thanks