Ufone only offer BB service with Post Paid connections, some other providers I have heard that do provide it with Pre Paid connections too.
Also there have been some restrictions by PTA on BB service at the time FaceBook PK closure and many apps do not work any more, browsing do not work same way any more as well, although I have rarely used FB app on BB but its not working either along with other Apps except Email service which I mainly use and thus still paying keeping the BB service. Ufone support say its form PTA and they can't do anything. Hearing rumors of more restrictions/closure of BB service in PK soon like UAE , though its just word of mouth so can't sure if its true.
With PrePay connection few things should work, Email with some third party app and browsing with some third party browsers.
@rnathbatra , I have BB curve 8320 , I will test it on another prepay sim on weekend and will try to update here how it goes when I get a chance.