[Skunkworks] ZTE Safaricom modem

Hi guys, I have a ZTE Safaricom modem (model MF637U ) and 1.5GB of data on my safaricom line. But anytime I try to connect to the internet, I get this message. *A connection to the remote computer could not be established, so the port used for this connection was closed.* What could be the problem? Regards Richard Gathogo.