You can also try going to a Casa de Cambio (a bigger one) and try to set up an account there for wiring money. Usually much cheaper than taking it out of ATMs (fees and currency conversion).
Not all of them do it - you have to have one that the cambio is kind of a side business - the ones who accept transfers are the ones who trade in currencies.
You might try Alhec Group - Paraguay 641. Sometimes you have to be reffered to someone before they'll let you open an account and transfer money.
The account isn't a bank account, it just identifies you so they can know which transaction is yours and they give you cash, usually in your preferred currency.