Thank You for your advise. I've visited Santander on Reconquista and they also have english-speaking staff.
But now a new problem occured. The requirements for a basic business account is: DNI and and a copy of any bill paid by me (any other than mobile phone i.e gas, electricity, cable). I don't have any, I rent an apartment temporarily and all the bills are sent to the owner's office (different address). It seems like I have no options here, the bank doesn't accept Certificado de Deomicilio neither.
Maybe you guys know a bank with less restrictions/ or accepting Cert de Domicilio?