My iPhone tells me unable to connect to my wifi programme

my iPhone is using the latest update but for some reason the wifi is not connected and when I

try to get it to connect it says Unable to join the net work which is ii136500primary to which my iPad connects as does my computer

I cannot understand why the iPhone which always used to connect to it now doesn't....the only alteration I have made to the iPhone was

to unlock it from Telstra but havnt removed the sim card etc as yet