I am an MEI (Individual Microentrepreneur), and I don't have a "contrato social" (social contract). What document should I submit?

As an MEI, you do not have a Social contract, as you cannot have partners. Instead, you should provide your Certificate of Microentrepreneur Individual Condition (Certificado da Condição de Microempreendedor Individual – CCMEI). This document serves as proof of your registration as an MEI, as established in Resolution CGSIM No. 16, dated December 17, 2009, and it replaces the need for an "Entrepreneur Application" for all purposes. 

In this case, please submit your CCMEI when opening your account with Higlobe.