Q: macbook wifi reset

I am in South Sudan so internet not brilliant.  I connected to a wifi network with my MacBook Pro and for a few days it worked perfectly.  There was a problem with the wifi, couldn't connect and others had the same problem.  Problem cleared for others but not me.  Could not log on to the network.  Checked the password (correct), tried with diagnostics and also removed the network using Advanced in diagnostics.  The network was working because I could join using my iPad so thought it a problem related to that network.  A day later tried another wifi network which I had used before and could not join.  With both I get a greyed out 'fan' with a small line through the middle.  Removing the network makes no difference so is there any way I can re-set the wifi within the OS (10.9.4) to clear the glitch?  A suggestion required urgently!