Iphone 4S WI-FI Issues

Over the past few days I have been experiencing numerous problems with the WI-FI on my device.

• Connection is very unstable. Keeps disconnecting, also very slow.
• When I scan for networks, the circle spins not picking up any available.
• If I turn WI-FI off, it grays out and I can not turn back on.

This is not a constant problem, it comes and goes 2 - 3 times a day. It will be working fine and then all of a sudden it collapses.

Some of the things I have tried.

• Resetting Network Settings
• Restarting phone. Home + Sleep
• Resetting Router.

This is not a problem with my router as other apple devices have no problems while on the network.

All help welcome.

Thanks,

Steven