‘Sunwai’ serves as one-window operation for customers. Customers can lodge their complaints related to any product. The each complaint is assigned a unique tracking number. KARACHI: The State Bank of Pakistan (SBP) has launched a customer complaint service portal and app ’Sunwai’. ‘Sunwai’ serves as a one-window operation for banking customers to register their complaints against Banks, Microfinance Banks (MFBs),